964 3.3T Performance Modifications
01-29-2010, 10:17 PM
#61
60 to 130 mph times. That sounds interesting. Maybe there should be a thread on that...
Kidding aside...60 to 130 mph runs do sound fun. Nice easy number to compare to others. I'd be all over that if I the risk of getting thrown in jail weren't hanging over my head. But to suggest this is a means of accurately and consistently generating a HP number is a bit far out there. Repeatability is hard enough on a chassis dyno let alone on the road. Backing into accurately saying how much power is made based on time from 60 to 130 is entertaining, but nothing more then that. To many uncontrolled variables. From a BS perspective...don't you think this stinks a little bit more then coming up with a number from a dyno, as it has over an over again?
Kidding aside...60 to 130 mph runs do sound fun. Nice easy number to compare to others. I'd be all over that if I the risk of getting thrown in jail weren't hanging over my head. But to suggest this is a means of accurately and consistently generating a HP number is a bit far out there. Repeatability is hard enough on a chassis dyno let alone on the road. Backing into accurately saying how much power is made based on time from 60 to 130 is entertaining, but nothing more then that. To many uncontrolled variables. From a BS perspective...don't you think this stinks a little bit more then coming up with a number from a dyno, as it has over an over again?
01-30-2010, 06:49 AM
#62
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I agree with James.
Jeff, if you send me one of those runs on AX22, I will tell you what is exactly your real HP and torque for every RPM throughout your run.. Those numbers will be what your car really is putting, no dyno BS.
01-30-2010, 10:55 AM
#63
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The laws of physics do not get suspended in the exhaust systems of our cars.
The more that the gases are forced to change direction, the more backpressure is created.
The turbine will be affected by the backpressure at the exducer face in the form of sluggish response. To make matters worse, the factory reduced the diameter of the pipe from the exducer to the tailpipe to 2.75 in. (the exducer diameter is 3 in.) The gases need to expand after doing work. Instead the stock system is trying to compress the gases into a smaller diameter.
It should be intuitively obvious that a straight thru muffler of the same diameter as the exducer and minimum turns after the turbine will offer less backpressure than the stock set-up, stock muffler included. Additionally, calculations will support this.
I expect that this topic is one of the many things that will be debated endlessly in cyberspace and is one of the reasons why I hang out here
The more that the gases are forced to change direction, the more backpressure is created.
The turbine will be affected by the backpressure at the exducer face in the form of sluggish response. To make matters worse, the factory reduced the diameter of the pipe from the exducer to the tailpipe to 2.75 in. (the exducer diameter is 3 in.) The gases need to expand after doing work. Instead the stock system is trying to compress the gases into a smaller diameter.
It should be intuitively obvious that a straight thru muffler of the same diameter as the exducer and minimum turns after the turbine will offer less backpressure than the stock set-up, stock muffler included. Additionally, calculations will support this.
I expect that this topic is one of the many things that will be debated endlessly in cyberspace and is one of the reasons why I hang out here
01-30-2010, 11:17 AM
#64
https://rennlist.com/forums/993-turb...ghlight=60-130
I agree with James.
Jeff, if you send me one of those runs on AX22, I will tell you what is exactly your real HP and torque for every RPM throughout your run.. Those numbers will be what your car really is putting, no dyno BS.
I agree with James.
Jeff, if you send me one of those runs on AX22, I will tell you what is exactly your real HP and torque for every RPM throughout your run.. Those numbers will be what your car really is putting, no dyno BS.
I would like to do a 60 -130 run though as I dig the speed thing. Looking at my gear ratio's I would have to shift twice as the top of 4th is ~120 mph. Now where can I find a road to run the test...
01-30-2010, 11:22 AM
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We are talking around the subject now. The turbo hasn't changed. You are still limited by the compressor map, which for a K27 means max of 77% efficiency (I used 100% for quick and dirty calc). So you simply are not going to get the figures quoted above.
Now assuming we can argue about this all day, lets put it to bed and compare actual performance figures. After all, this is why we bother to modify in the first place. Jean has a lot of data and a very accurate model that will tell you your real BHP.
Now assuming we can argue about this all day, lets put it to bed and compare actual performance figures. After all, this is why we bother to modify in the first place. Jean has a lot of data and a very accurate model that will tell you your real BHP.
01-30-2010, 11:29 AM
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Jeff, Jeans' model is very accurate and compensates for most things. On turbo's you are governed by Boyles law. This makes the biggest difference to recorded BHP. Dyno's simply do not load a car enough, for long enough, to get an accurate BHP reading. The temps just don't get hot enough.
I believe Jean can offer a good approx to real BHP with speeds lower than 60-130, i'm sure he will comment.
I believe Jean can offer a good approx to real BHP with speeds lower than 60-130, i'm sure he will comment.
01-30-2010, 11:44 AM
#67
We are talking around the subject now. The turbo hasn't changed. You are still limited by the compressor map, which for a K27 means max of 77% efficiency (I used 100% for quick and dirty calc). So you simply are not going to get the figures quoted above.
Now assuming we can argue about this all day, lets put it to bed and compare actual performance figures. After all, this is why we bother to modify in the first place. Jean has a lot of data and a very accurate model that will tell you your real BHP.
Now assuming we can argue about this all day, lets put it to bed and compare actual performance figures. After all, this is why we bother to modify in the first place. Jean has a lot of data and a very accurate model that will tell you your real BHP.
And as far as your dirty calc using the compressor map, there are other system limitations in play. Specifically the headers and mufflers. The factory headers run forward, merge into one pipe then back to the turbo. Exit the turbo through the cat and into the muffler. The aftermarket system is back directly to the turbo and out a straight through muffler. Hence making the motor a more efficient air pump. Just offering up my dyno'd (non 60 - 130 mph run) experience for others to digest.
Cheers,
Jeff
01-30-2010, 11:52 AM
#68
Jeff, Jeans' model is very accurate and compensates for most things. On turbo's you are governed by Boyles law. This makes the biggest difference to recorded BHP. Dyno's simply do not load a car enough, for long enough, to get an accurate BHP reading. The temps just don't get hot enough.
I believe Jean can offer a good approx to real BHP with speeds lower than 60-130, i'm sure he will comment.
I believe Jean can offer a good approx to real BHP with speeds lower than 60-130, i'm sure he will comment.
What type of dyno experience do you have?
01-30-2010, 12:25 PM
#69
https://rennlist.com/forums/993-turb...ghlight=60-130
I agree with James.
Jeff, if you send me one of those runs on AX22, I will tell you what is exactly your real HP and torque for every RPM throughout your run.. Those numbers will be what your car really is putting, no dyno BS.
I agree with James.
Jeff, if you send me one of those runs on AX22, I will tell you what is exactly your real HP and torque for every RPM throughout your run.. Those numbers will be what your car really is putting, no dyno BS.
I do dig that thread and have followed it for a while, as the numbers some of these high HP cars are simply amazing. This is after all where the rubber hits the road and there is no pretending...shortest time wins!
I like Colin from 9Meister's point below....so I'll copy and past hear. Summarizing....using an acceleration run can only "predict" engine HP. As he says the results are "meaningless" without the model. These variables as we know need to be estimated (type of road surface, rolling resistance, air density, rotational inertia, etc) to back into that final number. The possibility of an error hear is simply much greater then over accelerating a drum from one speed to another (assuming a chassis dyno). There's a reason tuners want to be on a dyno rather then on a road.
I do like the 60 -130 timed runs as this is very much about the area under the curve. The more area the more acceleration available....good stuff.
It's no mystery car Richard, just a well tuned 930 on K-Jet. I'm just using it as an example as to why on the road acceleration data is meaningless unless we can build mathematics into the the results which correct for different vehicle mass, transmission loss and aero properties. In my opinion the best that a 60-130 measure can hope to attain if you know the mass and bodystyle of the car is a guide to the available power (at the tyres) on the day it was tested. Unfortunately nobody seems able to use the current data to do anything other than prove who's car is faster than another, which is a little shy of being able to predict the true engine hp.
All I am saying is that I do not like snake oil, but if we can get our brains around this there is the possibility that we can produce an accurate mathematical model that can predict the engine hp of any Porsche from the 60-130 acceleration run time. If I remember rightly, the equations governing vehicle motion give the following:
Power to accelerate mass (overcome inertia) Pa = V x M x A
Rolling resistance power Rr = M x g x (R0 + R1V + R2V^2 + R3V^3)V
Aerodynamic power = Af x Cd x V^3 x D/2
where
V = velocity
M = total mass
A = acceleration
g = 9.81 (acceleration due to gravty)
R0,1,2 = rolling resistance coefficients
Af = frontal area
Cd = coefficient of drag
D = air density
If someone knows what proportion of the power is used to overcome inertia, drag and rolling resistance at any given speed it should be possible to predict the effect that a 10% increase in mass would have on the cars acceleration. Similarly for different body shapes, eg 930/965/993tt. Therefore predicting tyre hp should be relatively accurate, as should predicting the improvement in 60-130 time from a reduction in mass. This way we can all make an educated decision whether to re-tune the engine or simply leave the wife at home because she has a "negative effect on the inertial resistance"...
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All I am saying is that I do not like snake oil, but if we can get our brains around this there is the possibility that we can produce an accurate mathematical model that can predict the engine hp of any Porsche from the 60-130 acceleration run time. If I remember rightly, the equations governing vehicle motion give the following:
Power to accelerate mass (overcome inertia) Pa = V x M x A
Rolling resistance power Rr = M x g x (R0 + R1V + R2V^2 + R3V^3)V
Aerodynamic power = Af x Cd x V^3 x D/2
where
V = velocity
M = total mass
A = acceleration
g = 9.81 (acceleration due to gravty)
R0,1,2 = rolling resistance coefficients
Af = frontal area
Cd = coefficient of drag
D = air density
If someone knows what proportion of the power is used to overcome inertia, drag and rolling resistance at any given speed it should be possible to predict the effect that a 10% increase in mass would have on the cars acceleration. Similarly for different body shapes, eg 930/965/993tt. Therefore predicting tyre hp should be relatively accurate, as should predicting the improvement in 60-130 time from a reduction in mass. This way we can all make an educated decision whether to re-tune the engine or simply leave the wife at home because she has a "negative effect on the inertial resistance"...
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01-30-2010, 09:02 PM
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Chassis dyno numbers vary so much they are only good for personal comparrison between mods, a 60-130mph test, whilst knowing the cars weight is a way better way of working out your 'actual' power. Running the car from 0 up to flat out would be even better, as you can then see how the car is dealing with heat, and whether your power is staying with you.
Jeff, you said "it takes me longer to spin the dyno up under load (in 4th gear) then it does to accelerate to red line in 4th gear on the road". In which case how can the dyno give you an accurate figure? For it to be accurate it would need to exactly replicate the car on the road, or am i missing something?
Would be cool to see your 60-130!
Jeff, you said "it takes me longer to spin the dyno up under load (in 4th gear) then it does to accelerate to red line in 4th gear on the road". In which case how can the dyno give you an accurate figure? For it to be accurate it would need to exactly replicate the car on the road, or am i missing something?
Would be cool to see your 60-130!
01-31-2010, 08:16 AM
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OK, so I dug out my old dyno graphs. All done on same Dyno Dynamics dyno, owned by G-Force.
300.0 BHP, rear wheel. 1 Bar spring, K&N Panel filter, no Cat, no Muffler. Well tuned CIS. My WUR failed and this was fixed along with 1Bar spring. I can provide invoices /dynos if people really need, that details the work and ties out with the dyno sheets.
Ordered Headers from IA, fitted at G-Force and redyno'd. All other mods as above. 307.8 BHP, more boost, delivered earlier and over-boost to about 1.1bar in mid range. Over-boost took CIS out of optimal range and was approx 0.9 Lambda, but was near enough at peak BHP. Boost dropped to approx 0.9bar at peak BHP.
Stock brand new muffler was fitted after a few weeks as it sounded harsh. Gave up with CIS and moved to EFI.
Jeff, do a 60-130, we have plenty of stock 964turbos we can compare too.
300.0 BHP, rear wheel. 1 Bar spring, K&N Panel filter, no Cat, no Muffler. Well tuned CIS. My WUR failed and this was fixed along with 1Bar spring. I can provide invoices /dynos if people really need, that details the work and ties out with the dyno sheets.
Ordered Headers from IA, fitted at G-Force and redyno'd. All other mods as above. 307.8 BHP, more boost, delivered earlier and over-boost to about 1.1bar in mid range. Over-boost took CIS out of optimal range and was approx 0.9 Lambda, but was near enough at peak BHP. Boost dropped to approx 0.9bar at peak BHP.
Stock brand new muffler was fitted after a few weeks as it sounded harsh. Gave up with CIS and moved to EFI.
Jeff, do a 60-130, we have plenty of stock 964turbos we can compare too.
01-31-2010, 12:01 PM
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Jeff, on a dyno, different operators or different methods on the same dyno can give you wildely different results. We have seen this clearly in several cars with different tuners.
G-Techs are great fun tools, I used one for a couple of years as well. The problem with them is their lack of reliable accuracy, and this is why a GPS based datalogger is more appropriate, it reduces variables such as tilt impact etc...
All of these are taken care of and caluclated with the appropriate formulas, except wind conditions obviously, we try not to go out in windy conditions for realiability of data. Drag and friction and tire sizes, weight, gearing, etc is all calculated for every RPM point and every 1/10th of a second.
What Colin said and quoted above are the basics around the way the model was built, it includes quite a few things more, and can also tell you what the impact of additional weight, different gearing, aerodynamics, tire sizes etc.. will have on your acceleration data for the exact same car. The only problem with accuracy is with downforce (not drag), on high downforce cars, it becomes practically impossible to calculate HP at high speeds. I am talking about cars such as the CGT, or full race cars such as CUP or RSRs that have over 100KGs of downforce at high speeds etc..
If you do have access to a GPS based datalogger, I can look at your data if you wish, most interestingly would be before and after mods for example 
What Colin said and quoted above are the basics around the way the model was built, it includes quite a few things more, and can also tell you what the impact of additional weight, different gearing, aerodynamics, tire sizes etc.. will have on your acceleration data for the exact same car. The only problem with accuracy is with downforce (not drag), on high downforce cars, it becomes practically impossible to calculate HP at high speeds. I am talking about cars such as the CGT, or full race cars such as CUP or RSRs that have over 100KGs of downforce at high speeds etc..
03-11-2010, 07:08 AM
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When you start the engine after sitting overnight how much smoke is normal? I do get a bit but it clears and does not do it after a min or two. no smoke when warm and running at all.
Im going through everthing before any mods. CIS is next
Im going through everthing before any mods. CIS is next