Quite a few had requested this post, so here it is.

Chad,
All of Vr's dyno numbers on the website are engine dyno numbers.
Markski's were chassis dyno stuff off of a local dynojet.
Markski's engine seemed to produce approx. 80-100hp at any given level of boost as compared to Vr's.
At 1.5 bar, Vr's should have shown about 790rwhp, vs. 871rwhp on Markski's.
For direct comparison, I have a 1.1 bar run on Vr's on the website showing 744.6 crank hp at 7300 rpm's. At 16psi (1.1 bar) on the dynojet, we saw 733.97rwhp on Markski's with 624.96lbs/ft of torque. So, if you took about 18% off of Alex's crank#'s at that boost pressure he should have made around 610.5rwhp and 557lbsft of torque on the dynojet as compared to our engine dyno #'s... But then again, is 18% a correct correlation??? When you're dealing with dynojet's, they're purely an inertia based dyno vs. a load bearing engine dyno. So, your guess is as good as mine... We don't really have a direct comparison.
Driving both cars, Markski's makes insane power on top, where Alex's is a much smoother/flatter power curve.
Both cars max out around 1020-1030crank hp, basically just running out of fuel injector. they both have much more fuel pump/fuel system than that, just not any more injector. Alex's running out of fuel around 1.75 bar, where Markski's is out at 1.5 bar, both making about the same peak power levels just at different boost pressures due to the different efficiencies. The cars have great idle, cruise and power, so it seemed like a good place to stop. They can both regulate their power levels via electronic wg control, Alex's down to around 650hp at the crank minimum and Markski's to about 685rwhp (you can guess at the crank hp#) while maintaining very nice afr's at any given boost pressure.
In general, to produce the same power, the evoms cars have been making considerably more torque than we've been showing due to the smaller turbo's. They're running quite a lot more boost to obtain the same power, thus the higher torque level. High boost has always been a mortal enemy of head gaskets, studs and piston rings, so we always try to maximize the efficiency of the system and produce as much power under the curve and at a low boost pressure that we can. Not to say that their method doesn't hold merit, as it does. They make very nice boost response, great torque, and good power numbers. It's just a very different method and needs to be appreciated as such.
Not everyone wants to run 8200 rpm's like Markski's car, but he was well aware of that and was into the r's, where a current setup we're building is running gt3071r's vs. the gt35r's and will be revlimited to about 7300rpm's.
We build to customers liking

 

Good post Todd!

 

Awesome post Todd!

 

Really interesting, thanks Todd!

all the best
adam

 

Thank you Todd, BTW nice avatar.

 

When the mad scientist gets going....

Well I must accept that it took a while to digest all this data, what makes things even more confusing and almost uncomparable is the chassis vs. engine dyno data being compared.

I think Todd has raised two very important points, 1) How inaccurate chassis dyno readings are and 2) High boost vs. low boost tuning philosophy.

For point 1): I am a big detractor of chassis dyno readings, and I think Todd's findings here just prove why. One needs to look at torque and not HP in order to identify whether readings make sense or not. HP is simply a function of torque and not vice-versa.

Torque is a function of VE (Volumetric efficiency), boost and displacement, therefore 2 engines (with the same boost and displacement) will have VE as the only variable when it comes to torque readings. Things like better air intake, optimum combustion (through good ECU tuning) and exhaust flow, improve VE, this is where Todd K. focuses his efforts.

Let us look at some data that will help us identofy why a chassis dyno reading is almost meaningless as an assessment of performance:

- A stock 996 N/A engine has about 260 ft.lbs of torque at atmospheric pressure i.e. no boost.
- A stock 996TT has about 414 ft.lbs of torque at circa 0.6 Bar, a ratio of 1.6 vs. the N/A counterpart, and it also has an effective boost increase of 1.6 as well vs. atmospheric (no boost) conditions, the math works so far.


- Markski's engine has shown about 740 ft.lbs of torque at the crank ( 625 at the wheels) at 1.1 Bar of boost on the dynojet. The ratio of torque vs. the stock Carrera engine is 704/260= 2.7. This means that Markski's car should be running 1.7 Bar of boost to reach the torque levels that the Dynojet is showing, instead of the 1.1 Bar that it did run. While there have been serious modifications done to the engine, efficiency (VE) might have been improved by a maximum of 10% over a factory engine (I am sure Todd can confirm), but the dynojet numbers here show a 55% improvement.

This (50% increase in efficiency) certainly is not performance you will be seeing on the street, the chassis dyno will look very nice however for sure...

Which brings me to the the second point...High boost vs. low boost...The above chassis dyno numbers will be even more mistaken if you run high boost.

Torque being a function of VE, boost and displacement, simply by increasing boost alone, one can increase torque..simple? Yes but...this will last until the heat generated by the turbos heat soaks your engine and ICs and boost is no longer blowing CFMs, just hot air. Most likely you will not see this markedly the duration of a quartermile run since there is no real load on the engine. Load seriously starts in 4th-5th-6th gears, and I do understand that this is probably not what 90% of people care about anyway since speed limit and trap speeds in 4th gear hardly will let the car run heat soaked My post is purely from a technical POV.

Therefore, IMO an engine running lower boost ALWAYS has more upside potential for torque than one running higher boost, provided the components (turbos, ICs, etc..) are there to sustain the higher boost when crancked up.. The second point is that 2 engines producing the same torque or HP numbers, the engine running lower boost will ALWAYS sustain the performance longer, when quartermile is not the only objective for instance.

Different tuning philosophies indeed, each applicable to different purposes I guess.

 

I am not a piston head but none the less very enlightening and informative post.

 

Thanks Todd.Re Jean's point about relative worth of chassis dyno compared to engine dyno-- is it a correct presumption that you having(or soon to) will be in a position to do direct comparison with the same engine? Or is cost out of the question?

 

+ Rep for you

 

good info, thanks Todd

 

Yes, we will do that.
However, our chassis dyno is a dynapack, not a dynojet, and the dynapack is a load bearing dyno just like our engine dyno where the dynojet is an inertia based dyno. So, our comparisons will only relate from our engine dyno to our chassis dyno and others that share the same dyno's. Those with dynojets will be forever lost...

Case in point, put a stock car on a dynojet (inertia based) and on our dynapack (load based) to get a baseline. Take the same car and put a lightweight flywheel package on it and redyno the car. The dynojet will show more hp even though you haven't changed the power at all where the dynapack will show the same power.

Sure inertia has to do with acceleration rates. There's an interesting paper I sent over to Jean from Sachs about their clutches and the inertia change relative to track/acceleration rates. However, if you dyno your car in each gear, it will show different power outputs due to the changing acceleration rates of the rotating parts, where again, your power hasn't changed, just the inertia. So, is the dynojet really measuring power? Not really, just acceleration rates that they're back calculating power from. But they're not taking into account the inertia of the vehicle or components. Where load based dyno's measure the torque output vs. the accel rate and can better calculate the actual power/torque of the engine.

Yes, the light weight flywheel will make your car accelerate quicker, but has it changed the power? no, and will it make it accelerate more quickly in 6th gear? So miniscule that it would be hard to measure, but the more powerful car will run away regardless if it has the lwf or not...

Sorry, enough rambling ;p

 

Please ramble away- interesting points. It comes back to the point that anybody that knows anything about dyno's keeps making-- in summary -- there is no universal absoloute fact (in relation to dyno numbers) . Unfortunately it suits some( not aiming anywhere in particular) to attempt to use those numbers like that,wether for publicity,marketing etc . I was recently in workshop of world expert(generally acknowledged and record to prove it) non Porsche workshop and in discussion of these sort of points pulled out dyno sheets for what they refferred to as"1 minute" /"2 minute"/"3 minute" etc engines all putting out extrordinary numbers --- they scoffed at ever using that type of number-- they were doing genuine research and development for practical purposes.The problem we see on the forum is that many want to believe in absoloutes without seeming to comprehend the compromises made in getting those numbers.

 

Very Informative Todd, thank you for that data!! Rep for ya Bro..

 

"High boost has always been a mortal enemy of head gaskets, studs and piston rings, so we always try to maximize the efficiency of the system and produce as much power under the curve and at a low boost pressure that we can."

It seems to me that maximizing efficiency is the hallmark of Protomotive tuning.

It was pointed out to me that if one looks at the 1/4 mile time/trap speeds stickied at the top of the GT2 section, one will notice that the number 4 and 5 cars are Protomotive tuned. Note that they, as a general rule make much less horsepower (and are based on stock internals) than the cars ahead of them and many behind them even though the relative trap times and speeds are close. Why? Although I am certainly not an expert, it seems logical to deduce that what Protomotive is exceptionally good at is getting maximum performance from each and every hp/pound of torque.

 

I believe Viscious makes a valid point here.Whether it be a NA high compression motor or a low compression turbo motor or a combination of both it all comes down to cylinder pressure.Alex's motor making about the same hp but at a higher boost level is not a really bad thing as long as his turbos aren't out of their efficiency range.In fact, I would bet it makes torque earlier as a result of him having a little more restrictive head and cam setup while spinning less rpms.Just different in my opinion and looking at the boost pressure alone is not the tell all end all!