JohnEd

iTrader: (1)

I spoke with a few people around here that said that the 93 SC400 was rated for 250 HP but actually put out only 225. Can anybody speak with authority on this?

I went up to Portland, Or to the Unichip "factory" and dyno lab today. Great bunch to do business with and even better to listen to on matters automotive. Because stuff happens, they were only able to run my car without the new Unichip installed and tuned. At least I have a baseline of stock performance for my car. My crank HP peaked at 243.5 at 5,400 rpm. If what I was told about the SC being over-rated by Lex I am doing well. I can only attribute any gain over stock to my having replaced my center resonator with a piece of 2.5 inch tubing. That move netted me a reduction of 1 psi of back pressure.

Doest anybody know what the HP loss should be in the automatic transmission?

Thanks all

John

TheMole

iTrader: (13)

Maybe you heard that the 225 was the WHEEL horsepower and not from the CRANK. Wheel horsepower is what matters because that is the power going to the pavement. Just have your car dyno'd to get horsepower at the wheels. Parasitic loss through an auto tranny can have a certain range, but I have heard around 20-30%.

O. L. T.

iTrader: (17)

moved again.....

mkorsu

No. The general consensus is that the factory rating of 250 was rather generous. This based on the fact that most bone stock cars dyno'd at roughly 180-185 rwhp. Using a roughly 20% parasitic loss rate for automatic transmissions nets you roughly 225 crank HP.

JohnEd did have his car dyno'd, though I don't understand why they gave crank hp??? This was not a chassis dyno John?

Even so. With crank hp of 243.5 the result is roughly 195 rwhp.

JohnEd

iTrader: (1)

MK,
Yes, it was a chassis dyno and no, I don't know why they quoted crank hp. I'll find out next Friday when we have all the parts to do a final tune. I have more than complete faith in these guys and they have treated me like a blood relative for reasons I don't understand. Couldn't be happier about it though.

I think the crank quote is high for stock and I am sure it is honest/accurate for them. I was chalking the extra HP up to the ex mod that eliminated back pressure in the back half of the system.

Jack Friedman quoted me the same 18% loss in the auto as you estimated. I also know that these dynos are not putting to fine a point on it in terms of accuracy. I was amazed at how much a ten degree change in ambient air temp changed the HP numbers. You don't just run'er up on a dyno pass. You need some smarts and experience to interpret these numbers.

Their dyno is state of the art, 4 wheel drive, in the concrete floor...DYNO!

Can you tell me how many hp I shouildgain with a ex back pressure drop of 1 psi?

Thanks,

John

mkorsu

I really couldn't say how many HP increase the 1psi reduction would yield. Not my area of expertise, but I would think that it would net a few ponies.

What model dyno was this? Mustang? I forget which model offhand, but one model does normally yield results higher than others. I think its the Mustang Dyno.


But, yes.....proper tune, ambient temp, even using stickier tires can alter the outcome on a dyno!