indi9xx

Porschefile, I will look into this some more... Over here everyone except inertia dyno's run their runs in 3rd gear.

Yes, this one was really in 3rd gear.

I may call DynoDynamics and Dastek (both these dyno manufacturers tell me to run in 3rd) ask them some direct questions about this... Maybe they have a roller or encoder RPM limit for some reason and they give other excuses.... hmmm..

eastendr

I've done many runs on that dyno and results are no different in 3rd 4th 5th gear - the software compensates without glitch. That's one of the best things about the DD cells.

A really good result for Paul, Jon & Simon. It laid down line-on-line curves while Chris was setting up the boost controller.

You can nearly hear the car gasping for breath as it runs up the rev range - the AFM's strangling it at the moment so expect some improvements soon!

He's got 90 lb/Ft more than me already!

Rick.

eastendr

I believe the roller speed limit is 150 MPH, to 5th gear runs are out and 4th is starting to push it when you up the rev limiter.

More detailed graphs are HERE temporarily and I'll update the whole data table probably on Monday on Tuesday HERE

HTH

Rick.

indi9xx

Thats what I had heard about DD rolling roads Rick, same reading in any gear so its said to be best to just stick with 3rd for shootout mode..

It would be nice to get to the bottom of why some people get higher figures in 4th on other rolling roads on the other side of the atlantic.

333pg333

Hey Paul and Jon, that's great news and results. Unbelievable for it's first Dyno run under it's present setup. Can't wait for the follow up charts.
Congratulations.

tommo951

Duke,

Sorry I disagree here mate. No way does he want short runners. He is going for Torque not huge RWHP and a power band above 5000rpm. If he starts fitting short runners he will lose a lot of the low end torque he now has. The breathing is always going to be the restriction for Paul until he gets rid of the AFM and standard airbox. Remember it is on a map for running in that is essentially a 2.5 mapping. RWHP is just like a newspaper headline on its own. Torque is what gets you past a long truck when a car is approaching in the other direction faster than you thought!
Great work Paul and Jon, can't wait for the next episode!!

Porschefile

Like I said, higher gears load the engine more, which causes quicker spool, which will affect the powerband. Though, I was thinking Dynojet or inertia dynos when I posted that. I'm not as knowledgeable about variable load dynos like the DD or Mustang. Since the load is variable, it's always possible the operator could load it in 3rd gear to compensate for the different load the gear itself would have on the motor.

Porschefile

Torque doesn't mean a thing if you don't have hp. Chevy's from the 80's weren't fast even though many of them had 300-350lb/ft of torque as some of them (even Vette's) only made like 180-220hp. With Paul's motor being a 3.2l, it will generate plenty of torque even with an extremely short runner manifold. The runners don't need to be THAT short though. With runners a few inches shorter and a plenum that is considerably larger, it will flow a heck of a lot more above 5k rpm. I mean, why go to the trouble and expense of building a massive displacement custom motor when all you get out of it is really nice peak torque for ~700-1000rpm? It may FEEL fast, however it will be severely lacking on the top-end, so it might not be that fast overall. The higher in the rpm you can maintain torque, the more hp you will make and the more work you are getting done, so the faster your car will be and ultimately the WIDER your powerband will be.

A.Wayne

Porschephile , like the avatar , have done quite a few myself. alot of HP with T/Q

RolexNJ

I agree Patrick, get job! These guys did a fabulous job with Paul's car, and it isn't "optimallly" tuned right too, nor running higher boost if he wants too. I am glad to see that they did a great job, and built exactly what Paul wanted, which definately isn't a big RWHP beast. He wanted TQ and he got it. Good for them. That is some car, beautiful, stealth looking, and is making very, very impressive numbers too.

Cheers guys!

Duke

E X A C T L Y

A sudden rush of peak tq is the best way of fooling you that you have a really fast car...
To repeat Porschefile, tq alone without rpm's does nothing for acceleration or else we all would be driving diesels. Common sense, just compare power/tq to acc figures of petrol (UK talk here ) and diesel powered cars of the same model.

Regarding the runners, IMHO a good engine design is an engine with a wide powerband with a reasonable flat tq curve. A peaky tq curve is IMHO much worse than the Rennlist-detested peaky hp-curve. The runners on a 3.2l 4 cyl 8v engine would have to be like 50mm to make the tq curve even begin to look more peaky than flat.. You need much, much shorter runners on this type of engine to get a flat tq curve than on a 2.5l.

Anyway, once again Paul, congrats on the numbers and a beautiful car!
And indi9xx, I am impressed with the (at least in the 944-world) cutting edge and out of the box-thinking regarding the cylinder/piston/sealing stuff. Having the idea is one thing, but that it actually seems to work without leaking combustion pressure at 450 lbs of tq is a totally different thing

Now I'm back to building my cheap low budget 2.5l

tommo951

I think to compare a Chevy of the 80's to a Porsche 951 is like comparing apples to Presidents of the USA. I have a 7.1 litre V12 Jaguar engine that pulls 641bhp on the dyno but the torque figure is around 550lb+ from 2300rpm all the way to 6500rpm. I have done track days against lighter cars with hugew hp and at slower corners they just can't keep up, on faster corners they are changing gear and wasting time whilst I am accelerating away. Torque is key, if you get your balance right you will have reasonable RWHP figures but for driving fast on anything other than large ovals they are misleading as to how fast a car is.
Maybe we should start quoting standing 1/4 times or 0-100mph or 50-80mph in top gear times instead of RWHP figures as this is what really proves how fast a car is. Surely this is what matters?? Who agrees?

tommo951

And what won the LeMans 24 hours race this year? Yes an Audi diesel.
Which car recorded the fastest lap of the race? another Audi diesel.
With identical length short runners you are tuning for a specific rev/power range. This is why Porsche proivided unequal length runners. This was not an accident or a mistake. This was done to provide a balance of power and torque across the rev range. If you would like to discuss this off line PM me & I can provide you with the reasons including how it is not just the volumetrics that matter when calculating optimum runner length. But I promise you just running short runners will provide a one trick pony when you have a lot more available.
Food for thought if anybody wants to consider this is to open up the factory plenum and insert interference fit ram trumpets into the inlet runners (it is better if you actiually bore the runner to fit). This will give you better swirl characteristics as well as increasing the harmonic "charge effect"

Cheers
Tom

Duke

Although I disagree on many of your statements I won't turn this into a intake manifold design thread.

But you should know better than to give credit for a race car's lap time to the engine, diesel or not.

Please answer me this, do you disagree that it's the average horsepower in the used rpm-range that determines how fast the car will accelerate?

RennBod

Did I miss something or is this car really running a 2.5 modified chip, 2.5 exhaust, 2.5 intake and just about everything still 2.5?

If this is the case (I will re-read the whole thread later), this car is some serious scope for producing some MASSIVE figures (if 450lbs of torque isnt massive anyway!)

Well done Paul and all involved.

9XX/JMG service and modified my 964 turbo and did a great job, but these power figures from a 944 turbo are fantastic at this early stage.


I want one of these!