Geoffrey

I know there has been a lot of discussion regarding UK and USA dyno numbers with the suggestion that the latter being higher. I just completed my EFI Advanced class this weekend and saved some of the dyno numbers to show you here. The car is a completely stock 1987 924S with 119k that has the ability to run on stock Motronics or aftermarket Autronics. When running Autronics, the fresh air intake is retained, as is the air flow meter which is no longer used so all the restrictions are retained. The only difference is that the Autronic uses an MSD 6A to run the ignition, so it is CDI where the stock Bosch is inductive. However, since the inductive coil is retained, and the MSD products, are not the most powerful, I doubt this has much impact on the final numbers. Here is the final runs after the EFI Advanced students tuned the car for proper AFRs and maximum torque. The car gained approximately 14% improvement over the stock system. This was done using 87 octane fuel. I don't know what the drivetrain loss of a 924 setup is, but I would guess somewhere in the 25% range. The car stock is about 140hp, and using the Dynapack peak HP number of 107 computes to about 142hp at the flywheel. This is the same dyno i've done most of my other tuning on...Enjoy...

Ruf-Dan-Ruf

I had similar results with a 1986 NA 944 and a wire in Link computer system, around 14% increase, only tuning fuel. This was done on 96 octain.

The link was under $600USD so cheap HP.

Geoffrey

I would be surprised if you got a 14% power increase by tuning just fuel. I have not found that air fuel ratio makes much difference in power output as long as it is running in a reasonable range - 12:1 - 14-1 under power. It is the timing that makes the difference in power. In this case, the timing values are 5-7 degrees more than the factory and accounts for the power increase. In the class we do a demonstration where we hold the car at a particular RPM and Load say 3500 and 70kPa. We add fuel until it is so rich that it misfires and we remove fuel until it misfires. which in this car was 9.9:1 and 16.8:1. The difference in power over the range was 2hp from peak to the lowest. I have found that when doing a ramped run it affects the power more, but I suspect that is because of the charge cooling effect of the fuel moreso than the combustion process itself.

Ruf-Dan-Ruf

I agree 12 to 14:1 wouldn't see much difference. definitely agree on timing. We didn't have the timing hooked into the Link, only the fuel.

The car was running very rich. It was a race car. We leaned the car out from 11+-1 to around 13-1. The car had had some mechanical modifications exhaust, airfilter. We also removed some dead spots in the power curve by adjusting fuel in the zones. We had just below 100hp at the start and I believe we ended at around 112hp. Ignoring the numbers the difference from start to finish was around 14%.

On my race car I lean the car out on the track on the warm up laps before every race. The best/worst(depending on how you look at it) difference from one day to the next was 13% additional master fuelling from one day to the next. Afternoon race on Saturday was humoured warm sunny, next morning was cold and crisp but blue skies. I had to add 13% to master fual to get back to the magic 13-1. It was off the gauge (lean side) prior to adding more fuel and misfireing.

It sometimes gave me a huge advantage as not many if anyone I know does this.

I have a lambda link on my Porcsche. I see under all accelleration runs that it is 11+-1 all the time. This seems very rich from my experience. Do air cooled Porsches requirer the extra fuel for cooling??

I agree with your timing comments, I can feel the differnce of 1% advance on my racecar. I hate when we tune a new engine and have to pull timing out to stop detination.

Geoffrey

There are many factors that contribute to one engine requiring more or less fuel than another. You are using the fuel to manage heat in the engine and the air cooled Porsches need a little more fuel than a comparable water cooled engine.

Konstantin

< I don't know what the drivetrain loss of a 924 setup is, but I would guess somewhere in the 25% range>
It is 12-16%
<the timing values are 5-7 degrees more than the factory and accounts for the power increase.> and how much fuel If you do BOTH then you gain more. True just fuel do not do much on a Porsche unless it is a Turbo. then you see more difference.
<The link was under $600USD so cheap HP.>
You can modify the Motronic and it cost you nothing if you know how to do it :-)
@Geoffrey
does the power increase comes from teh Autronic or just by the timing increase? If you change teh timing in the stock Motronic you will still get an increase but not sure if you gain even more with an Autronic.-
have you tried to go over the 7 degrees and did you lowered teh timing at 3000 to 4500 rpm. This engine need at this area much less timing than at 6000.

Is it not possible to make your dyno to calculate the RWHP to FWHP?

Konstantin

Geoffrey

Konstantin,

I have not investigated the exact factors contributing to the power increase, but here are my thoughts on it.

I think that the majority of the power comes from timing optimization, hence my statement that you could reprogram the stock ECU with the timing values from Autronic and show similar power improvements. On my list of things to do is to send the timing values to Danno here on the board to see if he can burn a chip for me to test that theory.
The Autronic uses pressure sensing over air flow meter for load. While this just talks about where you are in the table, it may make a difference because pressure sensing is more accurate in the PV=NrT formula the ECUs operate on.
The Autronic is full sequential where the Motronics is batch fired. I have not seen WOT power gains from sequential over batch, I have seen throttle response in the low range and fuel economy improve. I doubt much if any power comes from this difference.
The Autronic is running an MSD CDI unit and the Motronics is using an inductive setup. The MSD is a weak CDI unit and since the same coil is used, I don't think there is a large gain in power from the CDI ignition system. Maybe 1-2%, but that is just a guess.

I did steady state timing tests to determine the proper amount of timing at each operating cell in the Autronic table. Timing was adjusted for maximum torque in the given cell.

I'd be surprised if the drivetrain loss was only 12-16%, but I've not measured it so I cannot really comment other than a guess of 25%. The Dynapack Dyno can show FWHP by adjusting the TCF parameter. If you thought the drivetrain loss was 12% you would enter 1.12 for a value in the TCF parameter. Since I always get beat up about dyno numbers, I just showed what the car produced on the dyno in terms of RWHP. FWIW, I posted this on the 944 board and they said I must be doing something wrong because the RWHP numbers were too low. I guess I can't win...too low, too high.

Woodster

geoff, you contributions are always informative and factual based. thank you!

Konstantin

Hello

I have a friend who use an Autronic in his 968 Turbo. He found much more Power after he switched to CDI. The car was runing lean and now he must upgrade his Injectors. This is only what I heard but I believe him and if he says the car makes more opower then it makes for sur emore power. BUT I do not know why?

If you want a modified chip for your 924S you can hav eone from me and if you want to reprogram your chip with you data give me the data and I can do that for you. Then you can compare all three chips and see teh difference

I can speak of a dynojet. 243c
The RWHP on a stock 951 is 190 vs 220 FWHP
for a Turbo S 215 vs 250 FWHP and so on. Since the 924S has a similar gearbox just not that strong I guess the RWHP loss must be about the same. Sometimes you must wait till the oil AND the gearbox oil is warm. Then you get more HP.
Is it a 924S with 2.5L or a 924 with 2L Your numbers sound right for a 924 but not for a 924 S. Did you put the same car on a nother dyno? Dynojet 243c. maybe teh car has a problem and delivers less power

Konstantin

Geoffrey

I believe that there is power to be found by installing a race quality CDI system compared to a STOCK ignition system, however, I don't consider an MSD 6A race quality, nor is a stock coil the proper coil to be running with a race quality CDI system.

I'd be interested in talking with you about a stock chip with the timing values from the Autronic.

As far as RWHP numbers from a Dynojet, they are known to read higher than they should be since they are using estimating torque from the acceleration rate of a known mass (the heavy roller). I would expect a Dynapack or Dyno Dynamics dyno to read lower.

The car is an 87 924S and I checked the car for leakdown and compression before I started this project and everything looks good. It does have 119k on it and still has a full exhaust with a cat. Gearbox oil can make as much as 10-15rwhp difference between cold and hot. These runs were done at the end of the day after running it for 6+ hours on the dyno with students practicing tuning.

Konstantin

you can contact me per email any time for a chip. I can have it ready for you within one day.
The soone rthe better since we build a Formula car and I have less time than usuall (almost zero)

Konstantin

Steve Weiner-Rennsport Systems

Hi Geoffrey:

Interesting discussion,.....

Just a note about the above. With all due respect, the MSD 6 series is a VERY good race ignition IF,...IF its proper configured & installed. Its well proven in a lot of serious race cars making well over 110 HP/litre as long as its deployed with the correct coil and all wired correctly.

These things will fire plug gaps that other ignitions simply cannot do and thats one of the keys for more HP. MSD 6's reliably fire .060 plug gaps in engines running over 1.6 bar of boost and N/A engines at CR's over 14:1.

This isn't to say that there are not inductive ignitions that cannot do that, its simply that MSD's (with the exception of the 5-series) are well suited for race engines of all types.

Everyone has their own experiences and I'd simply mention that MSD's (with big plug gaps) consistently make more power on our engine dyno (1000 HP Superflow) than anything else.

One last story,....many years ago we were running a 917/10 (5.4 litre) for a local client and the stock Bosch ignition simply couldn't keep all 24 plugs clear in that thing. The damn thing wouldn't idle for 15 seconds without fouling plugs. Since it wouldn't run with plug gaps more than .030 so we installed a pair of MSD-6AL's and matching coils. Even with the horribly cold plugs that these 917 turbo motors require, it idled like a CIS car and still ran hard at 2.0 bar,.....thats really big HP,........

m42racer

You have to look at the uses of the MSD CDI units. Yes there are better ones available, digital types that do not need to be converted to be triggered by EFI ECU's, but the MSD units power every NASCAR cup engine, I think and they are the 6 series. Sometimes we users get a little lofty in our stations because we use other more expensive systems, but the MSD units are very good value for money. That being said, I have used the MSD and two other digital types and my first choice would be digital. Excuse me while I climb down.