Boost
04-29-2004, 06:58 PM
#16
Range Master
Pepsie Lite
Lifetime Rennlist
Member
Pepsie Lite
Lifetime Rennlist
Member
What is your AFM reading at cruise say at 70 mph? sounds like you have boost, even when the engine is not under load. That is what the balooning of the rubber elbow indicates..............I agree with Lag..........too lean.
Be careful man........
Be careful man........
04-29-2004, 07:05 PM
#17
Drifting
Join Date: Jul 2002
Location: Los Angeles, CA
Posts: 3,348
Likes: 0
Received 0 Likes
on
0 Posts
The 4.5 cars, and donor engines, are so cheap, the whole "reliability" thing is not even valid. Anyone who can build a supercharged engine, can easily swap out their motor, if they blow it after 100,000 miles. Or even after 50,000 miles... The 3-4K for a replacement motor, is just part of the cost. And not a horrible cost at all, all things considered. The main thing to realize, is if you do a supercharger kit, and you blow a motor, you still have all the supercharger parts ready to go, for the next motor you put in... If these last even as long as the Calloway motors did, that may not be as reliable as the stock motor, but considering it is not too costly to replace a dead motor in a 4.5 car, it seems like a perfect candidate for boost experiments...
04-29-2004, 08:16 PM
#18
Three Wheelin'
Originally posted by bshaw
Why would it be too lean? It's well on the rich side of stoich.
Why would it be too lean? It's well on the rich side of stoich.
Currently, you are running high 13's, maybe 14:1 at WOT; those numbers are horrible for a NA engine, let alone one with a supercharger. The only thing that could be said of them is they would be considered 'rich' for cruise conditions.
At WOT, you want maximum horsepower, and that's produced at 12.5:1 air/fuel ratio. Since you're running a supercharger and intend to run it on the track, you need to run a tad more rich and why you should aim for 11.5:1. With that said, if you continue to run high 13's, low 14's at WOT under boost, you will blow your engine.
I'm not too worried about the blow off valve at the low boost levels I'm running, .
Corkey Bell in 'Supercharged' says it'll help cut down on noise but isn't as necessary with low boost levels in a supercharged system as it is in a turbocharged system. It's definately going on, but I don't think it's a critical item at this point in the game. If I was at 8 to 12 lbs of boost maybe, but not at 4 to 5 lbs.
04-29-2004, 08:28 PM
#19
Addict
Rennlist Member
Rennlist Member
Join Date: Feb 2004
Location: Monterey Peninsula, CA
Posts: 2,374
Likes: 0
Received 16 Likes
on
12 Posts
The 4.5 cars, and donor engines, are so cheap, the whole "reliability" thing is not even valid. Anyone who can build a supercharged engine, can easily swap out their motor, if they blow it after 100,000 miles. Or even after 50,000 miles... The 3-4K for a replacement motor, is just part of the cost. And not a horrible cost at all, all things considered. The main thing to realize, is if you do a supercharger kit, and you blow a motor, you still have all the supercharger parts ready to go, for the next motor you put in... If these last even as long as the Calloway motors did, that may not be as reliable as the stock motor, but considering it is not too costly to replace a dead motor in a 4.5 car, it seems like a perfect candidate for boost experiments...
How about if the system was designed properly in the first place..? Design out detonation, use quality components, and do lots of homework..... The engine lasts a lot longer, and your <cheap replacement motor cost factor and all the time you lose not enjoying driving the car> can go towards other things...
Why not just do it once, but the right way..?
Just my .02
How about if the system was designed properly in the first place..? Design out detonation, use quality components, and do lots of homework..... The engine lasts a lot longer, and your <cheap replacement motor cost factor and all the time you lose not enjoying driving the car> can go towards other things...
Why not just do it once, but the right way..?
Just my .02
04-29-2004, 08:58 PM
#21
Drifting
Join Date: Jul 2002
Location: Los Angeles, CA
Posts: 3,348
Likes: 0
Received 0 Likes
on
0 Posts
Because it is an understood fact that you will be working the engine a lot harder under boost.
What some people do not seem to understand, is that there is a contingent of 928 owners,
who prefer speed, over reliability. If we wanted reliability, or cheap repairs, we'd be driving a different sportscar. The 928 is a speed demon. It is a V8. It has a very high top speed. It has torque. It looks muscular. A lot of the owners of these cars like to go fast. Very fast. Now yes, we prefer something reliable. No one wants to blow up engine after engine, doing random experiments on a car that is so expensive to work on. So few people are just bolting on NOS, or turbos, or superchargers. People are trying to do their homework, and make kits that are reliable, and do not incur detonation, and are low boost, and intercooled. But for those people, the fact remains that the engine will not last as long as a stocker. There are too many factors involved. So if you can build it strong, it may last a long time. But even if you just boost a stock motor, it will still be pretty darned cheap to replace a 4.5, compared to replacing an s4 engine. My guess, is that if these cars are boosted correctly, they will last 50%-75% as long as a stocker. And if it is already old and tired, it might expire sooner than later. But still, what price will you pay to go really fast? If Bill's homemade supercharger kit is $2,000, and he blows his engine in a few years, he can get another engine, for $3,000, and put it in the car, and boost that one with his setup. So even with another engine in the calculations, he is still in the project for less money than others are paying for their MURPH kits. And there is no guarantee his engine will blow in a couple years. It may last 10 more years. Who can say? If he keeps the boost low, and keeps it in proper tune, it may be very reliable...
What some people do not seem to understand, is that there is a contingent of 928 owners,
who prefer speed, over reliability. If we wanted reliability, or cheap repairs, we'd be driving a different sportscar. The 928 is a speed demon. It is a V8. It has a very high top speed. It has torque. It looks muscular. A lot of the owners of these cars like to go fast. Very fast. Now yes, we prefer something reliable. No one wants to blow up engine after engine, doing random experiments on a car that is so expensive to work on. So few people are just bolting on NOS, or turbos, or superchargers. People are trying to do their homework, and make kits that are reliable, and do not incur detonation, and are low boost, and intercooled. But for those people, the fact remains that the engine will not last as long as a stocker. There are too many factors involved. So if you can build it strong, it may last a long time. But even if you just boost a stock motor, it will still be pretty darned cheap to replace a 4.5, compared to replacing an s4 engine. My guess, is that if these cars are boosted correctly, they will last 50%-75% as long as a stocker. And if it is already old and tired, it might expire sooner than later. But still, what price will you pay to go really fast? If Bill's homemade supercharger kit is $2,000, and he blows his engine in a few years, he can get another engine, for $3,000, and put it in the car, and boost that one with his setup. So even with another engine in the calculations, he is still in the project for less money than others are paying for their MURPH kits. And there is no guarantee his engine will blow in a couple years. It may last 10 more years. Who can say? If he keeps the boost low, and keeps it in proper tune, it may be very reliable...
04-29-2004, 10:34 PM
#22
Addict
Rennlist Member
Rennlist Member
Join Date: Feb 2004
Location: Monterey Peninsula, CA
Posts: 2,374
Likes: 0
Received 16 Likes
on
12 Posts
Hi There BC..
I beg to differ...!
I think my 928 is VERY reliable.. I have only gotten stuck once in 60k miles of driving. I know that it is a 17yr old car, and it was over 70k new, and maintain it accordingly. After having owned Ferraris, Mercedes, and other Porsche, BMW, and many other cars, the only other car that was as reliable was my S500, with my 740il a close second. I have driven this car to top speed many times, as I have with all my cars.
Now being that this vehicle is speed addictive, most will want to go faster. Thereby placing a higher degree of stress on the engine. Remembering that stresses on an engine are related in a higher proportion to the rotational speed of the components, then fast driving relates DIRECTLY to shorter engine life. Boost alone does NOT..! 100% increase in power from boosting ONLY PLACES 20% more load on the components of the internals. THIS IS NOT THE CASE with higher RPM....
Now, I cannot comment on others' ability to pay for these things, but I can surely say that if you are buying a budget car to go faster, then buy something other than a 928. The 928 is a very complicated automobile. however, in my experience, if maintained PROPERLY, it lasts a long time. mine has over 200k miles, and has never been apart.
I use my car daily, and drive between 150-200miles per day. Like I said, in 60k of driving this car recently, I have only gotten stuck once on the road.. That was from the fuel pump....
You have contradicted yourself by saying <<If we wanted reliability, or cheap repairs, we'd be driving a different sportscar. The 928 is a speed demon. It is a V8. It has a very high top speed. It has torque. It looks muscular. A lot of the owners of these cars like to go fast. Very fast.>>
and
<<But even if you just boost a stock motor, it will still be pretty darned cheap to replace a 4.5, compared to replacing an s4 engine. My guess, is that if these cars are boosted correctly, they will last 50%-75% as long as a stocker. And if it is already old and tired, it might expire sooner than later. But still, what price will you pay to go really fast? If Bill's homemade supercharger kit is $2,000, and he blows his engine in a few years, he can get another engine, for $3,000, and put it in the car, and boost that one with his setup. So even with another engine in the calculations, he is still in the project for less money than others are paying for their MURPH kits.>>
I have no relation to MURPH, but his design is good, that's why the engines have a lower chance of GRENADING, or lasting LONGER.
Now, about spending extra cash on a motor due to experimenting on a boosted motor with 5psi, just plain foolish, when Bill can take the same 5k and upgrade his basic well kept engine with intercoolers etc. and enjoy the car much more by eliminating detonation. FYI, DETONATION is the greatest cause of boosted motor failures. This is from POOR DESIGN....!
However, if Bill is foolish enough to start with a poorly maintained motor, he deserves to pay twice for stupidity or ignorance.. Whether it is Porsche, BMW, Mercedes, Chevy, Ford or any car. Engines are engines...! They all do the same basic things...! The science and technology exists to do supercharging properly at this time. If Bill or whoever does not, then Bill or whomever is asking to grenade his engine.
I beg to differ...!
I think my 928 is VERY reliable.. I have only gotten stuck once in 60k miles of driving. I know that it is a 17yr old car, and it was over 70k new, and maintain it accordingly. After having owned Ferraris, Mercedes, and other Porsche, BMW, and many other cars, the only other car that was as reliable was my S500, with my 740il a close second. I have driven this car to top speed many times, as I have with all my cars.
Now being that this vehicle is speed addictive, most will want to go faster. Thereby placing a higher degree of stress on the engine. Remembering that stresses on an engine are related in a higher proportion to the rotational speed of the components, then fast driving relates DIRECTLY to shorter engine life. Boost alone does NOT..! 100% increase in power from boosting ONLY PLACES 20% more load on the components of the internals. THIS IS NOT THE CASE with higher RPM....
Now, I cannot comment on others' ability to pay for these things, but I can surely say that if you are buying a budget car to go faster, then buy something other than a 928. The 928 is a very complicated automobile. however, in my experience, if maintained PROPERLY, it lasts a long time. mine has over 200k miles, and has never been apart.
I use my car daily, and drive between 150-200miles per day. Like I said, in 60k of driving this car recently, I have only gotten stuck once on the road.. That was from the fuel pump....
You have contradicted yourself by saying <<If we wanted reliability, or cheap repairs, we'd be driving a different sportscar. The 928 is a speed demon. It is a V8. It has a very high top speed. It has torque. It looks muscular. A lot of the owners of these cars like to go fast. Very fast.>>
and
<<But even if you just boost a stock motor, it will still be pretty darned cheap to replace a 4.5, compared to replacing an s4 engine. My guess, is that if these cars are boosted correctly, they will last 50%-75% as long as a stocker. And if it is already old and tired, it might expire sooner than later. But still, what price will you pay to go really fast? If Bill's homemade supercharger kit is $2,000, and he blows his engine in a few years, he can get another engine, for $3,000, and put it in the car, and boost that one with his setup. So even with another engine in the calculations, he is still in the project for less money than others are paying for their MURPH kits.>>
I have no relation to MURPH, but his design is good, that's why the engines have a lower chance of GRENADING, or lasting LONGER.
Now, about spending extra cash on a motor due to experimenting on a boosted motor with 5psi, just plain foolish, when Bill can take the same 5k and upgrade his basic well kept engine with intercoolers etc. and enjoy the car much more by eliminating detonation. FYI, DETONATION is the greatest cause of boosted motor failures. This is from POOR DESIGN....!
However, if Bill is foolish enough to start with a poorly maintained motor, he deserves to pay twice for stupidity or ignorance.. Whether it is Porsche, BMW, Mercedes, Chevy, Ford or any car. Engines are engines...! They all do the same basic things...! The science and technology exists to do supercharging properly at this time. If Bill or whoever does not, then Bill or whomever is asking to grenade his engine.
04-30-2004, 12:17 AM
#23
Instructor
Thread Starter
Join Date: Jan 2004
Location: Northeast
Posts: 172
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Gretch
What is your AFM reading at cruise say at 70 mph? sounds like you have boost, even when the engine is not under load. That is what the balooning of the rubber elbow indicates..............I agree with Lag..........too lean.
Be careful man........
What is your AFM reading at cruise say at 70 mph? sounds like you have boost, even when the engine is not under load. That is what the balooning of the rubber elbow indicates..............I agree with Lag..........too lean.
Be careful man........
I ran it to work and back today. I took it on the highway at lunch time and did a couple runs through the gears on the entrance ramps. Nice and smooth power, nice stable AFR with 8/10 leds on. I pulled the plugs tonight and they all looked nice and tan, but all were a darker on the side nearest the intake valve. No signs of fly specks.
I increased the injector constant a little tonight. It's running a bit richer now in open loop, in closed loop mode it just hovers around stoich. You guys got me worried :-)
04-30-2004, 12:34 AM
#24
Instructor
Thread Starter
Join Date: Jan 2004
Location: Northeast
Posts: 172
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Lagavulin
At WOT, the bare minimum air/fuel you want is 12.5:1, and preferably 11.5:1 which will help reliability by cooling the piston crown and chamber. Now that I'm thinking of it, you are going to be racing the car so 11.5:1 is the number to shoot for.
Currently, you are running high 13's, maybe 14:1 at WOT; those numbers are horrible for a NA engine, let alone one with a supercharger. The only thing that could be said of them is they would be considered 'rich' for cruise conditions.
At WOT, you want maximum horsepower, and that's produced at 12.5:1 air/fuel ratio. Since you're running a supercharger and intend to run it on the track, you need to run a tad more rich and why you should aim for 11.5:1. With that said, if you continue to run high 13's, low 14's at WOT under boost, you will blow your engine.
It doesn't matter what boost level you're running, you NEED a blow-off valve to dump the charge when you're out of boost and the engine is under vacuum.
Your assessment is incorrect. You will be making the supercharger work much harder than it has to which heats up the charge, as well as loading it's belt since it has to fight against compressor surge too. You must dump the excess charge.
At WOT, the bare minimum air/fuel you want is 12.5:1, and preferably 11.5:1 which will help reliability by cooling the piston crown and chamber. Now that I'm thinking of it, you are going to be racing the car so 11.5:1 is the number to shoot for.
Currently, you are running high 13's, maybe 14:1 at WOT; those numbers are horrible for a NA engine, let alone one with a supercharger. The only thing that could be said of them is they would be considered 'rich' for cruise conditions.
At WOT, you want maximum horsepower, and that's produced at 12.5:1 air/fuel ratio. Since you're running a supercharger and intend to run it on the track, you need to run a tad more rich and why you should aim for 11.5:1. With that said, if you continue to run high 13's, low 14's at WOT under boost, you will blow your engine.
It doesn't matter what boost level you're running, you NEED a blow-off valve to dump the charge when you're out of boost and the engine is under vacuum.
Your assessment is incorrect. You will be making the supercharger work much harder than it has to which heats up the charge, as well as loading it's belt since it has to fight against compressor surge too. You must dump the excess charge.
I'm not running 14.1:1 at WOT, not even close. I'm seeing 8 out of 10 LEDS lit at WOT, and it holds steady from when it goes open loop up to about 5500 RPM (I am staying away from redline for now). I did fatten up the fuel a bit tonight just to be on the safe side though :-) It's easy enough to back down a little as I gain a bit more confidence with the system.
And I wholeheartedly agree, I need to get the BOV/wastegate working for efficiency sake if nothing else. It's on the list with the IAC, VSS, IC, and WBO2.
04-30-2004, 12:42 AM
#25
Instructor
Thread Starter
Join Date: Jan 2004
Location: Northeast
Posts: 172
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Gretch
bshaw..........you gonna hurt that engine without a blowoff valve........finish the job before you go beatin on it any more.......
congrats, the install looks nice with the original spyder. "May the boost be with you"
BTW, show us your bracket.......................
bshaw..........you gonna hurt that engine without a blowoff valve........finish the job before you go beatin on it any more.......
congrats, the install looks nice with the original spyder. "May the boost be with you"
BTW, show us your bracket.......................
This pic shows the oil feed line, the oil drain (blue pipe out of the bottom of the SC), the belt tensioner, and the bracket from the drivers side.
04-30-2004, 12:45 AM
#26
Instructor
Thread Starter
Join Date: Jan 2004
Location: Northeast
Posts: 172
Likes: 0
Received 0 Likes
on
0 Posts
Looking straight down on the SC, you can see the bracket on the passanger's side on the left, and also going straight back (up) from the blue oil feed connector.
04-30-2004, 12:51 AM
#29
Nordschleife Master
One thing you need to know.
The AFM is NOT a linear relationship.
Blue lights do NOT always corrospond to rich conditions for what your aiming for. The narrow band O2 sensor tells you 3 things: if your rich of 14.7, at 14.7, or lean of 14.7. This corrosponds well to cruiseing conditions, when you want a mixture of 14.7 for emissions and fuel economey reasons, however, for boosted WOT application, 14.7:1 is BAD!
Thats it. It can not, and does no reliable tell you anything else. If your showing a "rich" voltage, your anywhere between 10:1, and 13:1. Where? You just don't know.
The AFM is NOT a linear relationship.
Blue lights do NOT always corrospond to rich conditions for what your aiming for. The narrow band O2 sensor tells you 3 things: if your rich of 14.7, at 14.7, or lean of 14.7. This corrosponds well to cruiseing conditions, when you want a mixture of 14.7 for emissions and fuel economey reasons, however, for boosted WOT application, 14.7:1 is BAD!
Thats it. It can not, and does no reliable tell you anything else. If your showing a "rich" voltage, your anywhere between 10:1, and 13:1. Where? You just don't know.