Race Car Exhaust

[markmac]

Those with more technical knowledge on the subject, this might make more sense to you.  Attached the one of the dyno sheets from one of the rounds we did, some of the exhaust info is listed there, not sure really what it means.  Also a pic of it on the dyno, lots of sh&t plugged into that thing.

[tzei]

Just out of curiosity... what CR and fuel?

 

Found the fuel: RON 118

Edited March 6 by tzei

[Preyupy]

WOW peak torque at 7500!  And you still have 160 lb/ft at 5800.  I'm impressed. 

 

Engine development is so much fun.  You can wear an engine out trying all of the different things and seeing what they do to the Torque/HP curves.  The simple ones are mixture and ignition timing. 

 

Then you try different cam timings (being a twin cam you have the chance to change overlap between the intake and exhaust)  I noticed you are at 102/106 deg how did you come up with that combination? 

 

You can also play with intake runner length by changing velocity stack length. 

 

Then the time consuming and costly trial of different header designs, runner tube diameter and length, collector size, exhaust system diameter and length, even mufflers.  And every time you change one thing you need to try all of the others again to see what is needed to optimize that configuration.  Then you get to figure out how to make it fit in the car.  

 

  Now that you have it all figured out pull the engine apart and freshen it up because you have just used up 50-60% of its life.  

[jimk]

It'd be nice to know the AFR per cylinder throughout the run.  Given the KF pump is quite constant cyl to cyl as it is a positive displacement  pump, the variation in AFR tells a lot about intake/exhaust variance cyl to cyl.

 

I see the fpr is controlling at 2.5 bar, whereas the Tii is 2.0 bar.

[markmac]

It's all engine builder guy.  I mostly just wrote the checks (alot of them).  As far as parts go, it has the best of pretty much everything.  Carillo Rods (148mm), CP Pistons, various coatings on the bearings, pistons, valves etc., Berrylium exhaust seats, Moldstar intake seats etc., etc.,  Cams I believe are 284's and the compression is 10.8:1 (pretty sure).  I wanted it built to make the most HP possible but not at the price of longevity.  My pockets are only so deep and not deep enough to have to 'freshen' things up every 20 hours.  As you noted Byron, 7500 is the sweet spot and I think that is a good number.  I know enough to know wear and tear goes up exponentially with the RPM's.  Really what we found was to make more power, we needed more cam, more compression and more fuel.  I am pretty happy with what I have really.

[Son of Marty]

8 minutes ago, markmac said:

Really what we found was to make more power, we needed more cam, more compression and more fuel. 

And more MONEY,  lots more money.

[markmac]

I may have posted these sometime ago, the dyno run/graph, has a comparison to a BMW M12/6 the my engine guy dyno'd.  What a friggin beast that thing was, but then to get up close to that 290hp number he had to take it to 9500rpm  The dark(er) red and dark(er) blue lines are the M12.  That thing just kept making power.  My engine was slightly better on torque, but then Schnitzer motors always were (are) 'torquier'.  Obviously, the control room is separate from the engine room, really loud in the control room so you can imagine what it would be like un-muffled.

https://www.youtube.com/watch?v=VzYu7fcOg98

Edited March 6 by markmac

[steve k.]

1 hour ago, Son of Marty said:

And more MONEY,  lots more money.

The first 20 horse power is cheap, the next 2 is expensive 

[Daily02]

What are you going to do exactly? Trackdays, wheel to wheel, timed competition? If you are doing wheel to wheel or timed competition backing off is out. Why prepare & pay to lose!

 

Are you going to run Laguna Seca on a 90db day? 

 

It will be of benefit to have different exhaust setups for different tracks. 

 

This is a challenging engineering problem, because you want it quiet and not eliminate the beautiful power output. The quieter system will add weight.

 

Now for the exhaust strategy. Create a system for the quietest track 1st.

 

Add mufflers in series.

 

Run the largest muffler cases that will physically fit (long & wide). Short small mufflers rob power & don't attenuate sound well. David Vizard has data on this.

 

The further back the mufflers are they will be more effective and less restrictive they will be as the exhaust gasses will have cooled and reduced volume. Mount the final muffler(s) beyond the rear of the car. This way you can remove them for the less sound restrictive venues. For a 2002 this will have at least 3 mufflers.

 

This will make for quiet lowest restriction system. 

 

Regards

 

Dono

[Daily02]

7 minutes ago, steve k. said:

The first 20 horse power is cheap, the next 2 is expensive 

Amen Brother!

[markmac]

Track days, it could run in any of the vintage events (but then I wouldn't be driving it). 

 

As far as winning (or losing those), since the car is a total bastard in terms of what run group it would go with, there isn't going to be any 'winning'.  Because of the high HP motor and European Gr2 everything else it isn't going to run with the B-Sedan boys and girls.  I would fully expect it to get thrown in with Porsche's (RSR, 935), BMW CSL's, and who knows what else.  Needless to say, it would be outpowered.  Steve Walker suffers this with the GS Car and M12/7 motor at pretty much every event.  Unless the 935 or RSR driver is a hack, you aren't ever going to 'win' over them.

 

I had considered what you suggest, essentially some sort of muffled system that could be changed out for a straight pipe.  I was figuring the connection point could be made somewhere in the raised tunnel area.  After that a resonator installed back towards the axle then a muffler on the other side (essentially where a stock muffler would go).  

 

I really can't see there being enough real estate for three mufflers/resonators.  The car is very low, 5-1/2" +/- outside of the raised floor area.  resonators/mufflers installed there need to really low profile and probably need to use oval pipe (maybe).  

 

One thing is for sure I am going to need to engage someone who understands race cars, and at the same time is a great fabricator.  Check this guy out, randomly came across his page on IG.  Holy smokes, the guy has some welding skills for sure.

 

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[steve k.]

Locally, Hoover at Turbohoses might be a good resource. He is in Livermore.  

If you already know what you want, finding a place that does exhaust for the 4x4 crowd is a good start. They know how to bend and tuck things as needed. 

 

If you do not plan on going out there and winning things, I would not worry about chasing the extra 2 HP by tuning the muffler location compared to the collector. That part might come later.

[markmac]

I used to be 'local', I hightailed it out of California and live in central Idaho now (a few miles south of Ketchum/Sun Valley), 2 hours east of Boise.  I have an 8' pile of snow in front of the garage where the car is so it won't be going anywhere for a couple of months.

 

Like I said, 'winning things' is relative in Vintage racing for the reasons I mentioned.

[TobyB]

Quote

WOW peak torque at 7500!  And you still have 160 lb/ft at 5800.  I'm impressed. 

Ha- I had the same reaction...  "Jeeezzzuzzzzz...."

 

t

[markmac]

And it idled at about 1200 rpm, which I thought was pretty remarkable for a mechanical slide throttle motor.