SlowGray hits the dyno...

[NCTURBOS]

Well, last night was the first time having SlowGray on a dyno (Dynojet), and I wasn't sure what to expect. I wasn't really there to get HP numbers but was more interested in the wide-band O2 numbers and how they compared to the Direct Scan data.

The car was tuned on the street for 18psi boost, and everything else remained the same as when it went 11.07 @ 123+ on 93-octane, except this time I had better octane in the car. Little did I know that due to less engine load (?) on the dyno the boost would be lower. Maximum boost on the dyno ended up being 15psi!!

The numbers:

443.73 HP
433.94 TQ

The A/F #'s were 11.5:1 across the whole pull from 3500rpm to 6000rpm. I'm running one of RA's Raptor MAF's and as far as metering the air and making corrections it was dead on. The A/F line on the graph is practically flat across the rpm range.

O2's were above .800mV the whole pull via Direct Scan.

The next outing with the car will be at the Norwalk event in Sept. We'll see how things progress from there.


K.

 

[Sweet6]

What heads and cam do you have?

 

[NCTURBOS]

Originally posted by Sweet6
What heads and cam do you have?

Champion ported iron heads & Weber 206/206 roller.

I just finished looking at the D/S file again, and the O2 #'s were actually in the .820's mV for the entire pull.


K.

 

[kenny]

Torque numbers seem low.

You shouldn't have seen any less boost.

 

[NCTURBOS]

Originally posted by kenny
Torque numbers seem low.

You shouldn't have seen any less boost.

Torque numbers are low due to the spool of the turbo being relatively slow. I'm working to change that here soon.

As for the boost, everyone I have talked to has said that if the dyno does not have enough drag on the drum to simulate the same load as on the street the boost will definitely be lower.


K.

 

[kenny]

With a dynojet you should never not have enough load.

At least, I've never seen it, and I've seen quite a few turbo cars on the dyno.

Nice numbers. Mine made similar.

 

[Dean]

Regarding the apparent low TQ #s, I have noticed that trend on many (all?) "cammed" engines. Engines with stock cams seems to have ~20-25% more TQ than HP, whereas cammed engines are more equalled.

 

[turbosam6]

Originally posted by Dean
Regarding the apparent low TQ #s, I have noticed that trend on many (all?) "cammed" engines. Engines with stock cams seems to have ~20-25% more TQ than HP, whereas cammed engines are more equalled.

That pretty much goes against 90% of what we see around here, at least with a "small" cam like his.

 

[ChrisCairns]

Originally posted by Dean
Regarding the apparent low TQ #s, I have noticed that trend on many (all?) "cammed" engines. Engines with stock cams seems to have ~20-25% more TQ than HP, whereas cammed engines are more equalled.

Cammed engines will go to higher rpm usually, therefore higher horsepower, everything else being equal.

A dyno can only measure torque. Then horsepower is calculated from that figure. Horsepower is ALWAYS higher than torque over 5252 rpm....and AlWAYS lower than torque under 5252 rpm. That's why you'll notice hp and torque lines on dyno sheets cross over at 5252.

The equation that the dyno's computer uses to calculate horsepower from torque is.....

HP = torque times rpm divided by 5252

So if you have 400 ft lbs of torque at 5000 rpm the horsepower is 380.8. If you take the same torque of 400 ft lbs at 5500 rpm the horsepower is 418.8.

 

[Dean]

You and I must be reading the same posts differently.

Can you direct me to some examples where this is not so? Not trying to be snotty or anything, it is just that I have been looking at dyno files for some time now as an educational tool for my own cam selection process.

I have ~30 files of dyno data so far, mostly from "Dyno Days" that our club has held over the last couple years. Some of the extreme HP:TQ spread are even more than the typical 20-25% that I noted... up to nearly 40%.

At the opposite end of the spectrum is a certain TT SBC (I won't mention the owner's name... it'll just turn into "one of those threads"), that recorded 15% lower TQ than HP... though he was smokin' the slicks on the rollers at that point!

Thanks,

Dean

 

[Dean]

Gotcha on that, Chris, and I agree and understand, but with the peaks, it is still a curious phenomena/trend that I have noticed. Peak TQ seems to always be down vs peak HP.

Dean

 

[85HOT-T]

That video of him smokin those tire was the coolest thing i have ever seen. Any one I have showed that to about $h!t thier pants. The sound alone is baffling