My bore will remain 95 mm!
03-31-2003, 01:50 PM
#1
Three Wheelin'
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My bore will remain 95 mm!
I just received word back from Millennium that the gouges on my block will be completely eliminated with the pre-machining process used for the Nikasil plating. Hence, the bore will remain 95 mm! This is great news, because I have the 95 mm gasket set and the rings I'll be getting are from a 95 mm 911 turbo piston. The other option was to go to 97 mm, but that little of an increase in displacement won't matter all that much...plus it puts me outside of the peak area of the IHI compressor map.
I can run more boost on the 4.5 liter displacement and have a higher efficiency than running the same amount, or less boost on 4.7 liters of displacment. It all has to work together!!!
The gouges were "only" 0.008"-0.010" deep, but this led to a leak down number of about 88% on my home made leak down setup. The other jugs all came in at 95% +/-
Bye Bye Alusil, hello Nikasil!
Next investigation: A BIGGER charge cooler!
I can run more boost on the 4.5 liter displacement and have a higher efficiency than running the same amount, or less boost on 4.7 liters of displacment. It all has to work together!!!
The gouges were "only" 0.008"-0.010" deep, but this led to a leak down number of about 88% on my home made leak down setup. The other jugs all came in at 95% +/-
Bye Bye Alusil, hello Nikasil!
Next investigation: A BIGGER charge cooler!
04-03-2003, 10:40 PM
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John: Whats the new motor going to make? Go for it and make some power. I think you can get 600hp out of "The Bastard" then go 993,996 twin turbo hunting. The twin turbo guys think they can run away from 928's.
George
George
04-04-2003, 12:02 PM
#3
Three Wheelin'
Please no offense intended George, but I do not think 600hp is realistic for an otherwise ‘stock’ engine as it would require a theoretical pressure ratio (PR) of 2.73, which is desired hp/existing hp which gives only a rough estimate. That rough 2.73 PR equates to an equally rough estimate of a little over 25 psi of boost. We can do a little better though so it’s not so rough an estimate and get us somewhere in the ballpark, even though it may be in left field.
We can use 2.73 PR as a starting point for determining how much boost is required for to attain 600 crank horsepower on a 4.5L/273ci, 220hp, 8.5cr, 80% volumetric efficiency for two-valve head, and conservative 6,200 max rpm. This engines stock airflow rate is 391.8 cfm.
To calculate the new hp and the boost required to attain it, we will use hp=original hp x new pressure ratio x density ratio x volumetric efficiency ratio x drive power efficiency. We need to know the ‘new’ hp so that we can keep adding ‘boost’ in psi and use the resulting pressure ratio in the calculation, and do this until we reach our theoretical 600 crank hp.
The theoretical boost required is 27 psi which gives us a 2.84 PR resulting in a required airflow rate of 1111.45 cfm which is simply the stock airflow rate x new PR. These numbers use a conservative 80% intercooler efficiency, 75% thermal efficiency on the tubos, and a ‘normal’ day of 90 degrees ambient. It goes without saying that 27 psi on an essentially stock 8.5cr engine is not a good idea for many reasons, one of which is the heat produced solely by the combination of boost and compression ratio which makes the combustion chamber temperature unacceptably high. It is worth noting however, that if the intercooler efficiency is bumped up to 85%, the density ratio jumps from .93 to .95, and the chamber temps now fall to an acceptable figure. This is only a theoretical figure and does not take into consideration the changes needed to the fuel and ignition components. The bottom line is that shooting for 600hp on a ‘stock’ 4.5L engine is not a good idea.
Reading earlier posts I think John said he would like to make 400 hp at the rear wheels which will require 433 crank hp which is 400hp + (220hp x .15).
Using the above stock engine configuration, our rough estimate pressure ratio is 433hp/220hp is 1.97, or a little over 14 psi, which we’ll use as a starting point to calculate what it takes to achieve 433 crank hp.
It will take 15 psi of boost, which gives us an actual PR of 2.02, and an airflow rate of 792cfm to hit 427hp. The heat produced in the combustion chamber solely by the combination of boost and compression ratio is very safe too. Again, this does not take into consideration the changes from stock required of the fuel and ignition systems, important considerations to say the least. But the calcs do provide an idea what’s required to get in the ballpark.
Now that we have a theoretical airflow rate, we can go about determining what is needed for the internal flow area of ‘A BIGGER charge cooler!’ core which comes out to be a minimum of 30 square inches using low density turbulators.
All calculations are Corky Bell’s.
We can use 2.73 PR as a starting point for determining how much boost is required for to attain 600 crank horsepower on a 4.5L/273ci, 220hp, 8.5cr, 80% volumetric efficiency for two-valve head, and conservative 6,200 max rpm. This engines stock airflow rate is 391.8 cfm.
To calculate the new hp and the boost required to attain it, we will use hp=original hp x new pressure ratio x density ratio x volumetric efficiency ratio x drive power efficiency. We need to know the ‘new’ hp so that we can keep adding ‘boost’ in psi and use the resulting pressure ratio in the calculation, and do this until we reach our theoretical 600 crank hp.
The theoretical boost required is 27 psi which gives us a 2.84 PR resulting in a required airflow rate of 1111.45 cfm which is simply the stock airflow rate x new PR. These numbers use a conservative 80% intercooler efficiency, 75% thermal efficiency on the tubos, and a ‘normal’ day of 90 degrees ambient. It goes without saying that 27 psi on an essentially stock 8.5cr engine is not a good idea for many reasons, one of which is the heat produced solely by the combination of boost and compression ratio which makes the combustion chamber temperature unacceptably high. It is worth noting however, that if the intercooler efficiency is bumped up to 85%, the density ratio jumps from .93 to .95, and the chamber temps now fall to an acceptable figure. This is only a theoretical figure and does not take into consideration the changes needed to the fuel and ignition components. The bottom line is that shooting for 600hp on a ‘stock’ 4.5L engine is not a good idea.
Reading earlier posts I think John said he would like to make 400 hp at the rear wheels which will require 433 crank hp which is 400hp + (220hp x .15).
Using the above stock engine configuration, our rough estimate pressure ratio is 433hp/220hp is 1.97, or a little over 14 psi, which we’ll use as a starting point to calculate what it takes to achieve 433 crank hp.
It will take 15 psi of boost, which gives us an actual PR of 2.02, and an airflow rate of 792cfm to hit 427hp. The heat produced in the combustion chamber solely by the combination of boost and compression ratio is very safe too. Again, this does not take into consideration the changes from stock required of the fuel and ignition systems, important considerations to say the least. But the calcs do provide an idea what’s required to get in the ballpark.
Now that we have a theoretical airflow rate, we can go about determining what is needed for the internal flow area of ‘A BIGGER charge cooler!’ core which comes out to be a minimum of 30 square inches using low density turbulators.
All calculations are Corky Bell’s.
04-04-2003, 03:14 PM
#4
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Reading earlier posts I think John said he would like to make 400 hp at the rear wheels which will require 433 crank hp which is 400hp + (220hp x .15).
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Actually, to make 400 RWHP you will need at least 470 crank hp(400/.85 = 470.588) considering 15% drive-line loss.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Actually, to make 400 RWHP you will need at least 470 crank hp(400/.85 = 470.588) considering 15% drive-line loss.
04-04-2003, 04:09 PM
#5
Three Wheelin'
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">quote:
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Reading earlier posts I think John said he would like to make 400 hp at the rear wheels which will require 433 crank hp which is 400hp + (220hp x .15).
--------------------------------------------------------------------------------
Actually, to make 400 RWHP you will need at least 470 crank hp(400/.85 = 470.588) considering 15% drive-line loss. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I figured that would raise an eyebrow or two since it goes against what a lot of people think as being true. According to the author, he contends that drivetrain loss is the same, at the same rpm, before and after a horsepower gain as nothing has changed in the drivetrain. Therefore to find the crank hp after an engine modification, take the new rear wheel dyno number and add to it the stock engine's original 15 or 20% drivetrain horsepower loss.
I am not trying to change anyones mind so do the calculation as you see fit. I will say that he has many years of experience to draw upon, something I myself do not have.
--------------------------------------------------------------------------------
Reading earlier posts I think John said he would like to make 400 hp at the rear wheels which will require 433 crank hp which is 400hp + (220hp x .15).
--------------------------------------------------------------------------------
Actually, to make 400 RWHP you will need at least 470 crank hp(400/.85 = 470.588) considering 15% drive-line loss. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I figured that would raise an eyebrow or two since it goes against what a lot of people think as being true. According to the author, he contends that drivetrain loss is the same, at the same rpm, before and after a horsepower gain as nothing has changed in the drivetrain. Therefore to find the crank hp after an engine modification, take the new rear wheel dyno number and add to it the stock engine's original 15 or 20% drivetrain horsepower loss.
I am not trying to change anyones mind so do the calculation as you see fit. I will say that he has many years of experience to draw upon, something I myself do not have.
04-04-2003, 04:51 PM
#6
Lagavulin,
I can tell you that the formula you are referring to will not give you RWHP as measured on a Dynojet chassis dyno. I have first hand knowledge with years of experience as well as empirical data that does not back-up what you are saying. If a car has 400 RWHP and you are using 15% driveline loss, you car hs 470 crank horsepower. So when a new 350 hp C5 Corvette with an automatic tranny dynos with 270 RWHP, should you sue GM for the lost power?
I can tell you that the formula you are referring to will not give you RWHP as measured on a Dynojet chassis dyno. I have first hand knowledge with years of experience as well as empirical data that does not back-up what you are saying. If a car has 400 RWHP and you are using 15% driveline loss, you car hs 470 crank horsepower. So when a new 350 hp C5 Corvette with an automatic tranny dynos with 270 RWHP, should you sue GM for the lost power?
04-04-2003, 08:13 PM
#7
Three Wheelin'
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">I can tell you that the formula you are referring to will not give you RWHP as measured on a Dynojet chassis dyno. I have first hand knowledge with years of experience as well as empirical data that does not back-up what you are saying.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Which formula are you referring to as I'm using around 20 seperate formulas to come up with my results. Are you also saying that you have years of experience dynoing 928 S's with blowers? If that's the case, what numbers did you get?
Using another reference go to this link and plug in 220 flywheel HP, 16 psi, 92 Octane, and 3-core intercooler.
<a href="http://www.superchargersonline.com/hp_calculator.asp?submit=1" target="_blank">http://www.superchargersonline.com/hp_calculator.asp?submit=1</a>
You will note it reports 425 estimated flywheel hp, which is close to my guess-timate 427 crank hp at 15 psi. Both calcs provide ballpark-only figures, a rough idea of what to expect when bolted together.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">If a car has 400 RWHP and you are using 15% driveline loss, you car hs 470 crank horsepower.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">That is true mathematically, but you don't mention whether that 400 rwhp is from a stock or modified car. That detail is important as the author asserts that drivetrain losses do not increase with a horsepower increase over stock.
The original example is a 220 crank hp car with a manual transmission that dynos at 187 rwhp with a resulting 33hp loss through the drivetrain.
After engine mods, the dyno now reports 400 rwhp. To get the crank hp, add the original 33hp drivetrain loss to the 400 rwhp and get 433 crank hp.
The question is, why should the drivetrain hp loss increase over the stock engine? The modified engine is still turning the same flywheel, clutch/torque converter, transmission type, differential, axles, etc. as the stock engine. Since it's all the same parts, why would it take appreciably more horsepower to turn them? In this case we are talking about a 70-33 = 37hp difference.
As I said earlier, if you don't agree, use what you feel is best.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">So when a new 350 hp C5 Corvette with an automatic tranny dynos with 270 RWHP, should you sue GM for the lost power?</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Your example has a 23% drivetrain loss. If any car is outside the accepted range of 15 to 20% loss, it is indicative of a problem which may require at the very least a tune-up, which may or may not be covered by a new-car warranty.
Let's suppose a car manufacturer has a one-size-fits-all computer tuning, regardless of whether that car is sold on the east coast, west coast, Denver, or Berlin. It makse sense that hp gains can be made by optimizing that car's engine management computer for the geological location in which it's operating. It also makes sense to forego spending $500(?) on a one-size-fits-all AutoAuthority(?) chip and instead spend that money on a reputable tuner who can dyno tune that unique engine to relative geological perfection.
Using another reference go to this link and plug in 220 flywheel HP, 16 psi, 92 Octane, and 3-core intercooler.
<a href="http://www.superchargersonline.com/hp_calculator.asp?submit=1" target="_blank">http://www.superchargersonline.com/hp_calculator.asp?submit=1</a>
You will note it reports 425 estimated flywheel hp, which is close to my guess-timate 427 crank hp at 15 psi. Both calcs provide ballpark-only figures, a rough idea of what to expect when bolted together.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">If a car has 400 RWHP and you are using 15% driveline loss, you car hs 470 crank horsepower.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">That is true mathematically, but you don't mention whether that 400 rwhp is from a stock or modified car. That detail is important as the author asserts that drivetrain losses do not increase with a horsepower increase over stock.
The original example is a 220 crank hp car with a manual transmission that dynos at 187 rwhp with a resulting 33hp loss through the drivetrain.
After engine mods, the dyno now reports 400 rwhp. To get the crank hp, add the original 33hp drivetrain loss to the 400 rwhp and get 433 crank hp.
The question is, why should the drivetrain hp loss increase over the stock engine? The modified engine is still turning the same flywheel, clutch/torque converter, transmission type, differential, axles, etc. as the stock engine. Since it's all the same parts, why would it take appreciably more horsepower to turn them? In this case we are talking about a 70-33 = 37hp difference.
As I said earlier, if you don't agree, use what you feel is best.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">So when a new 350 hp C5 Corvette with an automatic tranny dynos with 270 RWHP, should you sue GM for the lost power?</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Your example has a 23% drivetrain loss. If any car is outside the accepted range of 15 to 20% loss, it is indicative of a problem which may require at the very least a tune-up, which may or may not be covered by a new-car warranty.
Let's suppose a car manufacturer has a one-size-fits-all computer tuning, regardless of whether that car is sold on the east coast, west coast, Denver, or Berlin. It makse sense that hp gains can be made by optimizing that car's engine management computer for the geological location in which it's operating. It also makes sense to forego spending $500(?) on a one-size-fits-all AutoAuthority(?) chip and instead spend that money on a reputable tuner who can dyno tune that unique engine to relative geological perfection.
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04-05-2003, 01:55 AM
#8
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Lagavulin:
<strong>The question is, why should the drivetrain hp loss increase over the stock engine? The modified engine is still turning the same flywheel, clutch/torque converter, transmission type, differential, axles, etc. as the stock engine. Since it's all the same parts, why would it take appreciably more horsepower to turn them? In this case we are talking about a 70-33 = 37hp difference.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">For one thing, the amount of inertia the engine has to overcome to get those same parts to turn at an increased rate of acceleration is greater. The dyno masures power by the rate at which the car can accelerate the drums. It takes more power to accelerate those drums at a faster rate of acceleration. If you have any doubts, ask the manufacturers of the dynos if the drivetrain loss is constant or a percentage. After years of experience, seeing hundreds of dyno runs done, and even more charts, and talking to individuals who have done thousands of dyno pulls each, I'm in complete agreement with Jim.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"><strong>Are you also saying that you have years of experience dynoing 928 S's with blowers? If that's the case, what numbers did you get?.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'm sure an awful lot of people would be very interested to see the charts and numbers of those that you've dynoed. How many would that be?
<strong>The question is, why should the drivetrain hp loss increase over the stock engine? The modified engine is still turning the same flywheel, clutch/torque converter, transmission type, differential, axles, etc. as the stock engine. Since it's all the same parts, why would it take appreciably more horsepower to turn them? In this case we are talking about a 70-33 = 37hp difference.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">For one thing, the amount of inertia the engine has to overcome to get those same parts to turn at an increased rate of acceleration is greater. The dyno masures power by the rate at which the car can accelerate the drums. It takes more power to accelerate those drums at a faster rate of acceleration. If you have any doubts, ask the manufacturers of the dynos if the drivetrain loss is constant or a percentage. After years of experience, seeing hundreds of dyno runs done, and even more charts, and talking to individuals who have done thousands of dyno pulls each, I'm in complete agreement with Jim.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"><strong>Are you also saying that you have years of experience dynoing 928 S's with blowers? If that's the case, what numbers did you get?.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'm sure an awful lot of people would be very interested to see the charts and numbers of those that you've dynoed. How many would that be?
04-05-2003, 03:42 PM
#9
I never said I have dyno experience on a supercharged 928. My 928 has been tied-up in the hands of Devek's partner Lucky Ekman for over 2 & 1/2 years, but when it does come back I can start working on a custom supercharger system for my 928. I do have many dyno runs on the 928 with modifications as well as my custom supercharged Mercedes SEC. The percentage of driveline loss doesn't matter if it is a normally aspirated or has forced induction. The percentage loss is always expressed in percentage of RWHP. The higher your horsepower the more your driveline saps from overall RWHP. 
04-05-2003, 06:31 PM
#10
"The original example is a 220 crank hp car with a manual transmission that dynos at 187 rwhp with a resulting 33hp loss through the drivetrain.
After engine mods, the dyno now reports 400 rwhp. To get the crank hp, add the original 33hp drivetrain loss to the 400 rwhp and get 433 crank hp"
...Jeez. Thats absolutley Recockulous. 15% is taken FROM ANY number that is a realistic HP number for ENGINE HP. In the reverse, you add an approx 15% to RWHP to see what your engine is doing.
After engine mods, the dyno now reports 400 rwhp. To get the crank hp, add the original 33hp drivetrain loss to the 400 rwhp and get 433 crank hp"
...Jeez. Thats absolutley Recockulous. 15% is taken FROM ANY number that is a realistic HP number for ENGINE HP. In the reverse, you add an approx 15% to RWHP to see what your engine is doing.
04-06-2003, 11:45 PM
#11
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Lagavulin- I've got to say- you've obviously been around turbos and engines a bit longer than I have! Are you an engineer?
-Funny thing, pressure ratios: The turbine engines on the aircraft I fly typically have far higher quoted "pressure ratios" than what you've quoted- 9:1 with an airflow of 1500lb/second at max power [GE CF6-50].. Well, the Brayton cycle is a bit different....it runs typically 100:1 mixture ratio, whereas Herr Otto's contraption needs around 14.7-1 or so...
John doesn't want to change turbo sizes. So he is staying with 4.5 liters- something I would do too, but mainly for reasons of simplicity.
Interesting thoughts about intercooler sizes. You should post those formulas...
Dyno's change. Sometimes they read one thing, other days they read something else. From my flying, I'm skeptical about ANY gauge!
I've always heard that the drivetrain takes about 15% from power output...
It would be fun to see what typical 928's make...especially if other cars are there. This would allow us to see how much closer our hand-built engines are to quoted output compared to production line engines!
BUT the real thing that comes to mind, with regard to 600 hp...is the drivetrain. I would think that a 400 hp engine would probably not break the average 928 tranny or torque tube, but I bet that 500-600 hp would start to put some serious wear and tear on things, and might compromise reliability. Power is great, but you have to think about other things, such as clutches, gears, bearings, brakes, torque tubes...
Normy!
'85 S2 5 Speed
-Funny thing, pressure ratios: The turbine engines on the aircraft I fly typically have far higher quoted "pressure ratios" than what you've quoted- 9:1 with an airflow of 1500lb/second at max power [GE CF6-50].. Well, the Brayton cycle is a bit different....it runs typically 100:1 mixture ratio, whereas Herr Otto's contraption needs around 14.7-1 or so...
John doesn't want to change turbo sizes. So he is staying with 4.5 liters- something I would do too, but mainly for reasons of simplicity.
Interesting thoughts about intercooler sizes. You should post those formulas...
Dyno's change. Sometimes they read one thing, other days they read something else. From my flying, I'm skeptical about ANY gauge!
I've always heard that the drivetrain takes about 15% from power output...
It would be fun to see what typical 928's make...especially if other cars are there. This would allow us to see how much closer our hand-built engines are to quoted output compared to production line engines!
BUT the real thing that comes to mind, with regard to 600 hp...is the drivetrain. I would think that a 400 hp engine would probably not break the average 928 tranny or torque tube, but I bet that 500-600 hp would start to put some serious wear and tear on things, and might compromise reliability. Power is great, but you have to think about other things, such as clutches, gears, bearings, brakes, torque tubes...
Normy!
'85 S2 5 Speed
04-07-2003, 12:41 AM
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Normy; I think you are right about the drivetrain being a weak link. If it was me I would do it like abby's doing going with the vette 6 speed. I think the 6 speed is kick a$$. John go for 500hp!! good luck
George
George
04-07-2003, 01:23 AM
#13
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transmission losses are not linear. the more power you generate, the greater the loss due to friction, changes in gear tooth to tooth geometry (they separate and casue increased losses), heat buildup....all from increased loading.
So in conclusion, driveline loss increases in a non linear fashion the more power you attempt to transfer.
Marc
DEVEK
So in conclusion, driveline loss increases in a non linear fashion the more power you attempt to transfer.
Marc
DEVEK
04-07-2003, 01:48 PM
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I look at it this way....600 HP is probably waaaay out of question without dropping mad coin. My compressors will each support about 250-275 HP, maxing out at about 2.3 on the pressure ratio map.
I have been running lots of numbers for expected HP out of this engine. Yes, 220 HP was the stock number, with cat and air pump. Both are gone, so I figure maybe 230 HP without them. The Nikasil and (hopefully...) lighter forged pistons may free up an additional 10 HP, so with those mods alone, I might be looking at 240 HP without any manifold pressure.
Add in 14 psig of boost and an efficient charge cooler, and I think I'll easily hit the 400 crank horsepower mark, hopefully north of 450 HP at the crank. Anything over 500 will probably kill clutches and driveline parts. Of course clutch holding is based on torque, not necessarily power, so I am trying to be as conservative as possible. Marc from Devek probably has some thoughts on this.
This all depends on how much fuel I can get as well as ignition retard and charge cooler efficiency. I think 14 psig will be where the line is drawn, maybe even 12 or so, it all depends on how things work out on the dyno.
For now, the goal is to get the damn parts back and put it all together, then start playing. My design limit is 14 psig, so anything outside there is risky. Pistons, where are my pistons...?
I think my injectors will be able to provide 39 lbs/hr at 60 psig on the rail...I have to have them flowed to confirm. Nonetheless a larger fuel pump is required for some margin of safety.
On another note, I calculated the compression ratio at 8:1, not 8.5:1 as claimed by Porsche. 14 psig should be no issue, it is done on 944 turbos all day long...
The nice thing is I'll keep the stock redline on the engine (6200 rpm), none of this 7500 rpm stuff. For the power the car will be making at 5500-6000 rpm, the torque curve will be FAAAAAAT! Hopefully not too fat to kill clutches in a heartbeat though.
The whole package should make a very relaible and trick one of a kind 928, which is the ultimate goal.
I have been running lots of numbers for expected HP out of this engine. Yes, 220 HP was the stock number, with cat and air pump. Both are gone, so I figure maybe 230 HP without them. The Nikasil and (hopefully...) lighter forged pistons may free up an additional 10 HP, so with those mods alone, I might be looking at 240 HP without any manifold pressure.
Add in 14 psig of boost and an efficient charge cooler, and I think I'll easily hit the 400 crank horsepower mark, hopefully north of 450 HP at the crank. Anything over 500 will probably kill clutches and driveline parts. Of course clutch holding is based on torque, not necessarily power, so I am trying to be as conservative as possible. Marc from Devek probably has some thoughts on this.
This all depends on how much fuel I can get as well as ignition retard and charge cooler efficiency. I think 14 psig will be where the line is drawn, maybe even 12 or so, it all depends on how things work out on the dyno.
For now, the goal is to get the damn parts back and put it all together, then start playing. My design limit is 14 psig, so anything outside there is risky. Pistons, where are my pistons...?
I think my injectors will be able to provide 39 lbs/hr at 60 psig on the rail...I have to have them flowed to confirm. Nonetheless a larger fuel pump is required for some margin of safety.
On another note, I calculated the compression ratio at 8:1, not 8.5:1 as claimed by Porsche. 14 psig should be no issue, it is done on 944 turbos all day long...
The nice thing is I'll keep the stock redline on the engine (6200 rpm), none of this 7500 rpm stuff. For the power the car will be making at 5500-6000 rpm, the torque curve will be FAAAAAAT! Hopefully not too fat to kill clutches in a heartbeat though.
The whole package should make a very relaible and trick one of a kind 928, which is the ultimate goal.
