bobt993

HP/wght ratio is still the best option for the GT class. The modern cars can manipulate a dyno run easily, but to suggest someone would cheat on a dyno before they would cheat on class specs is really kind of silly. If someone wants to cheat, they are going to in any format and do their best to get away with it. Dyno at the track, add 25.00 to the entry fee for GT cars (they are saving thousands on the build by not having to build a monster). Offer compliance and cert at the track on a per run basis (fee generator). The dyno operators usually offer some free pulls to the race organizers as long as they generate enough income.

BTW, the black box placed in the car can be pretty acurate on measuring hp. Yes, you could dog it, but your laps would suffer.

jrgordonsenior

BGB used Mike Bavaro (Bodymotion) for their 3.6 Koni builds. They were pretty complete builds going .030 over with top of the line internals costing around $15k IIRC on top of core costs. With tuning they were gettting 325-330 rwhp out of those motors....

jrgordonsenior

They've been consistantly inaccurate on my car. In 2010 at Miller for NASA's Nationals the Trackmate black box lived in my car. They wouldn't tell me exactly what it read but said it was reading significantly more than the 3 dyno runs they had me do.

This year the So Cal chapter used it twice on my car at Buttonwillow before and after I ran on their Dynojet there. It read approximately 20 more rwhp more than the Dynojet results. They put one in a friend's 06' GT3 cup with 80 hours and a recent 380 rwhp dyno. It showed 412 rwhp.....

How do they accurately compensate for things like aero or braking?...

Ritter v4.0

[QUOTE
While I'd hate to get into the "my shop can do this for $x,xxx" game, it would be very interesting to toss a few numbers out; AC vs. WC and see where the rainbow falls.

It's well known that say $40K will get you a dyanamite 3.8 AC engine at 110hp/L and that this is just about the max build for a engine which will give dependable service over the course of two long seasons.[/QUOTE]

So is the comparison a/c 3.8L to w/c 3.6L?

KaiB

So is the comparison a/c 3.8L to w/c 3.6L?[/QUOTE]

Nope, I was thinking WC horsies vs. AC horsies, and dollar against dollar. Wide open, is are the GT classes at the moment.

The thought being, would my theoretical $40K AC engine trump your theoretical $40K WC engine and the weight handicap you must bear because of the larger multiplier. Longevity of each engine must be the same in our little excercise though.

analogmike

Another point to consider with air cooled vs water cooled is the chassis. The WC chassis are faster... better in low speed turns, better aero, etc.

bobt993

Mike your correct and that is one of the factors for the multiplier. Aero is free though so time to under the car. I just finished reading a good tech book on low speed aero and I know where my car is suffering from some of the theory and wind tunnel results they discussed. JR, I think the issue with the box is they need to look at your front straight 1:1 closest gear. The same one you would dyno at. If you look at lower Long A runs in say 2nd or 3rd gear they are going to be higher dyno results than your 1:1 ratio.

jrgordonsenior

Bob that's interesting on several levels. It reasons then that aero wouldn't have as much impact on the shorter straights either. When they dyno me at Buttonwillow on their Dynojet, they always use 4th gear which is a 1.216 ratio. 5th gear is 1.024. Should I insist on them using 5th gear?....

jrgordonsenior

[/QUOTE]
Nope, I was thinking WC horsies vs. AC horsies, and dollar against dollar. Wide open, is are the GT classes at the moment.

The thought being, would my theoretical $40K AC engine trump your theoretical $40K WC engine and the weight handicap you must bear because of the larger multiplier. Longevity of each engine must be the same in our little excercise though.[/QUOTE]

I think that's fine comparison since the 3.8 AC runs in GT3. The weight handicap in that example is only 375 lbs. I think you can get equal HP out of either motor. I know of 3.8 AC's can get in excess of 350 at the wheels as I've dyno'd them. Gamroth had a new 3.8 AC motor in his RSR at Rennsport. Id love to know what that monster puts out....

I've never seen or heard of a M96 putting out that much WHP. Maybe Jake of Flat 6 Innovations or John Tece of BGB, or Mike Bavaro of Bodymotion will chime in if they're reading this....

winders

Don't think dollar against dollar. GT classes are not "Spec Dollar" classes. You can spend as much as you can afford. An unlimited budget WC engine is going to destroy an unlimited budget AC engine. The WC engine will last longer too.

scott

KaiB

Gamroth had a new 3.8 AC motor in his RSR at Rennsport. Id love to know what that monster puts out....

I'll ask if I can say...I know. OK: A bit over 430@7600 and a bit over 325ft#@6250.

M758

Hey I remember back 10 years ago when all you had to do was to pull your interior and take out 100lbs and sent to GT where the only multipler was for turbo motors. I remember racing in GT4S in 944 spec car. 2600lbs, lightly modded (for GT standards) suspension and stock 2.5L motor putting out 130 whp. At the time the standard was 2100llbs and 2.8L 911 air cooled motors putting out 300 hp.

At least now my little 2.5L 944 motor would not be forced to compete head on with superlight 911/914 2.8L 911 motor any more.


HP/weight is the next step, but even then those with cash to burn will always have change to bring better equipment. The fewer the rules the money it takes to win.

No class is perfect.... even spec classes. I learned 10 years ago that if I wanted to run my car competitively on a budget I would need to find the right place for it. If that mean leaving PCA it meant leaving PCA.

M758

I can't say exactly how it works on regional level, but at nationals NASA pays to have mobile dyno on site for the event. They then get use of that dyno for any compliance runs NASA officals choose. Competitors do not have to pay for the dyno run. At least not directly as it figured in as a part of event operating costs. Of course when not use for NASA compliance competitors may rent time on the dyno payable to the dyno operator. One can presume that NASA would get discounted rate/fee structure and operator would expect a few competitors to pay for the service for tuning and make money that way.

So PCA could add mobile dyno to their races too, but it would probably need to funded by an increase in entry fees to ensure to the operator is worth is effort to bring out the equiment and his time spent. Yes that would mean that non dyno classes would in effect be forced to pay for the dyno class compliance. Of course this presumes there is a dyno operator in the area to draw in.

bobt993

YES!!!!!!!!!!!! bring your gearing chart. You can easily prove your gearing to be accurate by an rpm/speed run. Gearing does make a difference and that is why the closest ratio to 1:1 is the only way to normalize this, (but not any overdrive). I don't have an overdrive gear and run 6th at 1.03 with a taller tire and stock R/P setup. You will have guys state it makes no difference, but this is not true. I have a top notch dyno operator in our area who builds cars sent to him from all over the world and he sees a bit more power from other gearing used. The engine I am selling dyno'd at 284whp in 4th gear and around 274 whp in my 1.03 gear. I actually choked it down with an earlier computer and a muffler to get it down to 265 for a race in October. In July, I had a stock engine which detuned to 258, but it was not very flat in hp (peaky).

M758

I agree with JR... The black box idea is cool, but not ready for primetime. If it could be it would be major benefit, but I don't trust it now. Maybe in a year or 2 or 3? I know NASA is investing time and money into this and think it is good idea to explore it.