December Fastrack is out!

[erlrich]

Andy, what is that based on? Just stock horsepower with the usual 15 percent improvement?

Hey Andy, I know i am digging up an old thread but..
after doing some leg work, and speaking with Jeff about that 235 WHP that was used to class that car, I need to ask for a clarification. Was only one dyno test used?

My discussion with Z1 motorsports, one of the leading Z shops in the country, puts that power of a basic IT build in the 200 hp range at the wheels.

Here is also a link to the 300zxclub website where people put up their dyno numbers with, again basic IT mods. It again supports the 195 - 205 hp at the wheels, numbers.

http://www.300zxclub.com/showthread.php?t=78732

So how would I go about trying disprove the one dyno sheet (that I know of) that was used to classify the car weight?

Tristan - I don't know this for a fact, but knowing how the process works I would guess they used the standard formula for IT-prep HP; for the Z it would be 222 stock HP * 125% = 277.5, then using the generally accepted drivetrain loss of 15%, you would get 236 HP to the rear wheels.

As for proving the car DOESN'T make that much HP, you're in for an uphill battle I'm afraid. Of course, on the plus side the way the CRB is doing things now all you have to do is build the car and run 4-5 seconds slower than the top cars, and you'll be eligible for a weight break I would do that with the Camaro, but it's already too damn light...

[benspeed]

Tristan - I'm in the same boat although not as heavy with the 968. Based on the 25% gain I should make 236hp at the crank X 125% = 295 hp at the crank, less 15% driveline loss = 250 rwhp.

I am not remotely close to that number...but just had a top end motor job done so we'll see what she does on the dyno in a couple weeks. Regardless, there is no remote chance of 250 rwhp with a legal motor - even the FireHawk 968 cars make 235 at the wheels with race pistons, cams etc...

[Ron Earp]

Hey Andy, I know i am digging up an old thread but..
after doing some leg work, and speaking with Jeff about that 235 WHP that was used to class that car, I need to ask for a clarification. Was only one dyno test used?

I might very well be wrong but I think 225 rwhp. Not that it makes a lot of difference, hell, it actually makes the classification situation worse if it was 225 rwhp....

Either way, fixing it in the current climate would be tough.

[Jeremy Billiel]

Umm Ya.... Good luck with that.

[erlrich]

My discussion with Z1 motorsports, one of the leading Z shops in the country, puts that power of a basic IT build in the 200 hp range at the wheels.

Here is also a link to the 300zxclub website where people put up their dyno numbers with, again basic IT mods. It again supports the 195 - 205 hp at the wheels, numbers.

http://www.300zxclub.com/showthread.php?t=78732

Looking at the numbers posted on the Z website, it might not be as far off as you think. There are guys putting up numbers in the 205-210 range with just IT-legal bolt-on mods; it doesn't look like any of them have touched the internals. It also looks like most of those are street cars, so they're probably still sporting most of the pollution equipment. I would bet you could get 220-225 out of a full-tilt IT build (including engine management & dyno tuning). 235...might be a little optimistic. Problem is, there is only one way to find out.

EDIT: just for the hell of it, I re-ran the weight (per the process) using 225 at the wheels (265 at the crank), and it looks like the car would probably have been about 140 lbs lighter had that number been used. Also of interest, using the 277.5 crank HP number it looks like the car received about 130 lbs of weight after the base weight was calculated; i.e. the car's weight would have been 3122 just using the ITR pwr/wt multiplier, yet it is classed at 3250. I'm guessing it got rewarded for great suspension & brakes????

[Tristan Smith]

I guess I won't know for sure until I build a full blown engine. But even 220whp seems optimistic.

[tnord]

i was under the impression these cars made BIG gains with IT legal prep?

my 1990 had 222 stock hp;

222 * 1.3 = 289 * .82 = 236 - 237 whp.
222 * 1.3 * 11.25 = 3247

222 * 1.25 = 278 * .82 = 227 - 228 whp.
222 * 1.25 * 11.25 = 3121

yes, 18% driveline loss is used for RWD cars.

[lateapex911]

RWD cars have a 90 degree turn in the driveline that FWD cars do not, so the WHP is different. If you're going to do the math to back out the components, use 18% for driveline on RWD, 15% for FWD.

[erlrich]

So the 300ZX was classed using 30% for the HP increase? Interesting....

[JeffYoung]

Caveat -- I have an ITR 300ZX sitting in a storage shed.

What I know: the impression the motor makes big gains comes from a single dyno sheet on a car (my car I believe) from when it ran in SSA with a cat back exhaust. Supposedly made 225whp.

Like Tristan, I've not seen anything close to that in the research I've done, but the only way to find out is build an IT motor and see.

My guess is 225 whp in IT trim.

[JoshS]

So the 300ZX was classed using 30% for the HP increase? Interesting....

It appears to me (I wasn't involved, so I don't know for sure) that only about 1/3 of the ITR listings were done with 25%. Most are at 30%. There are some at 20% and 15% too.

[Ron Earp]

RE the 300zx - my cursory research showed that 200-210 rwhp might be hard to get BUT all that data I turned up was from the guys on Z boards who want to bolt stuff on and are strangers to the "every little IT mod is important and eventually adds up to big numbers". Didn't find anyone who had done the 0.5 compression, rings, hours on header design, etc. that it takes to make serious IT power.

In fact, the same Z guys laughed and called me a liar when I posted plots of our ITS Z's making 165-175+ rear wheel hp using stock cams and stock carbs. Go figure.

I bet a 300zx in 100% IT trim will be close to 225-235 rwhp.

[GKR_17]

Tristan - I'm in the same boat although not as heavy with the 968. Based on the 25% gain I should make 236hp at the crank X 125% = 295 hp at the crank, less 15% driveline loss = 250 rwhp.

The 968 was run through at 15%

[924Guy]

I'd definitely agree with the 968 having a low power adder, such as 15%, but the driveline loss should be more like 18-20%, same as the rest of us (924/944's) - that torque tube and transaxle eat up a lot of juice!!

[benspeed]

Ahmen to that, Vaughan.

What is the power adder for the BMWs?

What do folks think a 100% 968 should make at the wheels?

[Andy Bettencourt]

Ahmen to that, Vaughan.

What is the power adder for the BMWs?

What do folks think a 100% 968 should make at the wheels?

BMW's are getting 30%. In order to meet the process expectations, the 968 would be around 220 to 222whp.

[GKR_17]

What is the power adder for the BMWs?

All the ITR BMW inline 6's were set at 30% (every inline 6 got 30% in the original proposal). The ITR BMW E30 M3 got 25%... good luck with that.