I got a GSR swap awhile ago and that was semi-built (Blox B cams, 70mil TB, big tube header, JG pnp head, old-school ported S2 intake. This motor put down 215 whp/140 tq on a Dynojet at DNR. This was an open header run though.

I had everything put back to stock to BAR in my car. That's done, so I put in S2 tuner 2 cams, S2 Pro intake (not ported), kept the JG head, stock 60 mil TB, JDM 4-1 ITR header w/stock cat. Blacktrax did the work and tuning and got it up to about 175whp/118tq on a Dynapak. I'm wondering if the big tube header/no cat and the bigger TB and ported intake really makes that big of a difference. I'm having a hard time believing I would gain 40 whp by swapping headers, losing the cat, and porting the intake and using a large TB. I'm thinking I'm giving up maybe 15whp at the most.

Now, I know that different dynos read high/low, which is the point of my question. Has anyone here used both shops for dyno tuning? Which dyno reads higher? Blacktrax says their dyno tends to read lower than most of the bay area Dynojets, and that they rarely see an all motor B-series pass 200 whp on their dyno. I've seen anecdotal evidence online that it reads lower. But I'm wondering if anyone has had experience with both shops and can chime in?

fm

 

on my personal car, a 68mm TB and 62mm TB lost around 10 hp on a dynapack. and thats on a b20 non vtec. that was under the fact that the air fuel was retune from 68 to 62 and maintain the same ratio as when 68mm was on the car. recently, i change the exhaust setup, now the b pipe got a step down to 2 1/4 pipe/resonator, and that lost another 14 hp. so i wouldnt be surprised in your case u lost 40hp, coz all the mod u are doing is to increase air flow, and now the 60mm TB really reduce your air flow by alot.

 

Wow...going down from a what...2.5" exhaust down to a 2-1/4" cost you 14hp?

I had planned on putting on the 70 mil TB again, but the S2 mani is 64 and I'm not ready to port match them. I'm afraid that the 70 mil TB may actually hurt performance as the airflow won't be a smooth. Also, I'll need to do another tune if I increase the size of the TB. Another commitment in time and $$.

fm

 

Well, I can answer my own question now. I swapped out the JDM ITR header for the DTR, thus deleting the cat in the process (not really desired, but for the time being I have no choice). I picked up 10 whp, bringing me up to 185whp/120tq on Blacktrax' Dynapak. Without any tuning too...and as a result, there was about 15-20 ft lbs of torque lost at the VTEC crossover.

2 days later, I took the car and did a baseline run on DNR's Dynojet with the exact same setup, and it put down 192whp/127tq. So, Blacktrax' dynapak really does read lower than at least one bay area dynojet. Given that dynapaks have the reputation of reading highest of all of the dynos, I found this rather encouraging. Keep in mind that the weather conditions were the same...about 75 degrees F/50% humidity.

I went ahead and had DNR port match the intake's runners to the head and the port matched the TB opening port to the 70mil throttle body. I put it on the dyno and had it tuned...it ended up making 200whp/130tq. I'm pleased, and I imagine it'll put down somewhere in the 190s on Blacktrax' dyno.

The moral here is that not all dynapaks read high...it depends on how they're calibrated. I think the infamous Church dynapak may be responsible for this misperception.

fm

fm