Woodster

Great, great stuff!!

thank you Bill S, TB, and Jean (as well as KPG!) for getting us interested in this
great form of performance measuring.

Now will someone please sticky this thread at the top of the 993TT thread with
just the list of results in order!!
It is impossible to find out what everyone did compared to others
and include a few benchmarks like the ENZO or CGT New Z06 for comparison

thanks guys and WOW Marek!!!!!!!!!!!!

MK

Bill S.

Thanks so much! This looks pretty extreme. No mufflers or cats? I wonder why Protomotive would use cross-over pipes and not just go straight out from the Turbos? Must be loud!

P.S., Although my CA smog guys are pretty friendly, I'm not sure what they'd say if they saw that under the car!

Jean

I just wanted to give my opinion on a couple of the interesting points raised, warning: I am biased.

Concerning the Lag issue, the long Gs interpreted as lag up to 4K RPMs are rather traction problems. If we look at the difference between the two charts posted by Markski (100-200kph and 60-130mph) you will see that one of them starts at 0.3G at 60mph and the other at 0.5Gs. The difference in pull in my opinion between the 2 runs is traction loss, I could not explain it differently.
In fact, this second chart puts this car at the levels of the most powerful N/A, including the CGT at those RPMs...

Bill as far as your comments, the high RPM redline is only a bonus and not the way this car is extracting power, there has been a lot of work done on this engine to improve its efficiency without needing high RPMs or high boost...Let's not forget that the chart comparing it to KPG's very fast car, we are comparing a car pulling at 0.9 Bar vs. one pulling at 1.3 Bar, and in fact Markski's starts pulling on KPG's quite before redline. Needless to say that at 1.3 Bar Markski's car would have been way ahead from 70mph most likely. (sorry KPG )

As far as the short tracks and slow Protomotive cars, maybe you have had a different experience than mine? But my car has never suffered from lag at the track, or the one autocross I did...if my RPMs ever dropped below 3.5-4K, I should be one gear lower, otherwise I would need to take driving lessons Do you know whether that slow car on the trackwas a full Protomotive tune or was it a cut and paste hybrid build?

It is all about high HP and sustained torque delivery to go fast around the track and in straight line, rather than midrange torque or peak, on these turbo engines that have so much of it (more than a 996RSR at the lowest boost setting) the issue is rather how to control the car, you don't need more torque at low RPMS!

It also all depends on the objectives set, if I wanted a street car that pulls like a freight train without having to downshift, I would have fitted smaller turbos and a 9.5:1 compression, like some of those that Todd builds, however for track or high speed runs, certainly high Hp and high RPMs are king on turbo engines, and when coupled with low effective compression (factor of compression and boost) to keep heat soak as much under control as possible, it is a strong combo.

KPG

Jean, perhaps you missed the point. That graph was in no way challenging Mark's car, rather following up on a point TB made about lag with the big turbos...Having driven Mark's car at 1.4 bar and had the back end get loose at 110mph in 4th ... I would have to respectfully say that Mark's car at 1.3 bar in 3rd gear would be no faster, maybe even slower.All traction related...or lack thereof. I am sure Mark will chime in... Kevin

Jean

Kevin,

I know you are not challenging Mark , I was just commenting on the graphs you posted, on those graphs, specifically the 60-130mph, I don't really see important lag, maybe on others there is, but that is all I have seen.

If Mark's car is no faster at 1.3 bar, then there is a problem, and if it is a traction one, then his suspension/tire setup is sub-optimal or he needs to go to a better road ( I have experienced this often). He can sure get another second shaved from this time with some traction losses.
Cheers

markski

You guys I have major traction problems... those runs were done in high 30 degree temps. I even kept the PSM ON. I asked Todd and he said that the TB by default is in a different position just becasue the PSM is ON. I can not go full throttle at .9 bars let alone 1 bar in those temps without loosing traction...
To prove the point(its getting real cold here).... I will do some high end runs.... I just cant get the car to stick at 40 mph....
Jean, what do u suggest I do( what range in mph) would give you a good indicator of the cars power...
mark

TB993tt

Markski
Be careful out there mate........I am having multiple scary moments in our current conditions which are warmer and with far less torque.

Please go easy, you don't want the back end kicking out at high speed, I had a big moment in fourth gear at 90mph and don't want to think what might have happened if the tail had swung back the other way -these levels of torque in a rear engined RWD need massive respect..........wait until you get better conditions and the safest possible venue

markski

I know... all the close friends like Jean are telling me to be carefull.
I put 80Kmiles on this car b4 I did this... I had 3 other tuning kits... but it was not RWD and id did not have twice the power...
Ill wait till I get in the mid 40s... one day... maybe do a 3rd thru 5th gear.... if I start a little later.. like at 70 mph I should not have a problem at 1 bar or less....
I still have yet to turn the boost controller ON....
I have a evo 8 that is all built up.... it ran 10.2 1/4 at 137 mph.
I want to run both cars next to each other... should be interesting...
mark

Jean

Mark

What you have experienced during your runs is something we have had numerous discussions about TB and myself in private. we always asked ourselves, how can those 800HP claimed HP cars be driven? I know I have had a 3 lane change during one of my runs with semi-slicks, and TB had his share of them too. To a point that I have never done any more runs.

However, to answer your question about how far can one go with his engine and keep traction, there are quite a few variables in play. I have attempted to do an analysis with the data available to me through the posts here.

I have extrapolated the acceleration graphs in meters per second square (divide by 9.81 for Gs) based on your different three dyno runs, in third gear. All the data here is customized for your car when it comes to aerodynamic drag, tire sizes, weight, gear ratios and RPM limiter etc.. so the results should be "theoretically" meaningful. You will see difference with the datalogger data due to many factors, the most important of them being chassis dyno optimism.

These curves show the traction threshold for your car in thrid gear at the three different boost levels. The redline is the tire traction threshold assuming optimum conditions of grip for the tire (temperature, dry pavement etc..). This also factors a weight transfer of 80% to the rear wheels under accelertion.

During your runs, I would not be surprised if I saw that this threshold (red line) is more like 0.6-0.7 rather than 0.8. Meaning you have more traction loss than what this chart suggests at 1 Bar.



Based on the above, at 1.5 Bar you stand no chance of getting sustained grip, however since chassis dynos at high boost are typically 200HP off once the car is under load on the street, the threshold might be quite better than shown here as well.
You will be fine up to 1.1 Bar and most likely 1.2 Bar as long as you have good tire (pressure and temp) conditions and dry decent pavement. You have another second from your best time out there yet, only get those tires properly warm.

Increase your contact patch, put softer rear suspension and raise the car's CG by increasing the height (20mm is ok) and you might have a mass trasfer of 5% more to the rear wheels under acceleration, and you will have increased that threshold to 0.85Gs or more... not bad huh... There goes another 0.5 second from your times. Wonder why Eddie Bellos 911 drag car has an SUV like ride height and stock suspension?

Apologies if my post is not clear, I will be happy to explain further how the workings are done.

TB993tt

Jean
That sounds about right from my experience.
I posted this before:
https://rennlist.com/forums/showpost...99&postcount=1
It was ~6degC/42degF with 12" rears 315/30 tyres -traction broke as 0.678G was hit then the G peaked (a fraction of a second later) at 0.745.
The cold makes a big difference particularly since the tyres are summer tyres (mich PS2)

markski

You guys are both blowing me away....I don't get it.... but that's OK...
I'm new to this driftbox stuff....
markski

Jean

Mark

The redline is where your maximum traction is and the curves are where your car will be going in 3rd gear at the different boost levels, anything above the redline is traction loss This is not datalogger information but a calculation based on your dyno charts and car specifics.

You can make that redline move up or down by getting your tires to optimum temperatures, or a few other things that I mentioned above.

TB, the data seems to make sense indeed.

Bill S.

Thanks Jean. Here's some comments:

1. What do you think the Protomotive 60 to 130 would be if they shifted at 7200 RPM with 1.1 bar? That's comparable to a Ruf car with much more conservative boost and redline.

2. I define "Lag" as the time between depressing the throttle and getting the full power you would expect at the pre-throttle RPM. None of these plots show that lag because the throttle is always depressed and, at the shift, the turbo is not really winding down due to the bypass valve. I don't have direct experience with the Protomotive cars, but other very high-horsepower turbo cars I've seen have a 1-2 second lag. The CGT lag is nearly zero (i.e., the engine sounds like it "barks" at you when you press the throttle). That adds up when pressing and releasing the throttle on the track, as well as the overall enjoyment of the car. For example, I've heard a few people say that the CGT (and some other non-turbo cars), although not as powerful as the Protomotive cars, is very fast around the track and more enjoyable due to the zero lag.

911/Q45

Does all this traction difficulty lead us back to the AWD?

JJayB

Bill,
As much as some want to believe that their modified turbo cars have no lag, they do. It's realized when you start tracking your car against worthy opponents. I must admitt that I've had some pesky Vipers with steamroller tires give me fits, due to their "no lag". Understand when they get too much power, I gain a bit due to the all wheel drive. Hard to measure that on the driftbox, that's why they have race tracks.