I recently dynoed my max in Houston and was, to say the least, a bit dissapointed with the results. N/A it runs a measly 155 FWHP/181 FWTQ in 3rd gear and 156 FWHP/183 FWTQ in 4th. With a 65 shot being controlled by the JWT ECU, I put 246 FWHP/275 FWTQ in 3rd which is an additional 90 front wheel horsepower and 95 foot pounds of torque.

What's the deal? Why am I producing so little power naturally aspirated?

BONE-Stock I ran a 15.2 @ 90. Haven't run it since though but I'm really worried about the low numbers N/A

:attention

Here's the dyno plot link:

http://image1ex.villagephotos.com/1475931.jpg

 

Are you using the stock heat range plugs?

 

Yes, JWT said that the spark plugs need not be gapped. Are you suggesting that my issue is that a spark plug gap? If that were to be the problem, would not it affect me more from a Nitrous Oxide perspective and not NA.

I am basically pushing a 100 shot at the crank. Would a step or maybe 2 step down heat range help? If so, what is to stop the A/F from being so rich on the high end. In terms of fuel pressures and EGT...my fuel pressure goes up to 46 psi which above the 43 psi min required by JWT ECU. My EGT peak at about 1550 F on a both NA and while spraying.

What could be the problem?

 

Colder plugs will prevent detonation...they won't affect AF ratio. Generally, they are a good idea for the longevity of your engine when using some kind of forced induction (NOS or boost).

However, using colder plugs (espescially more than 1 step) will rob you of NA power, which is why I was going to suggest your NA numbers weren't great. However, I guess that's not the case.

 

So, what could be wrong my max? I have yet to do a compression test on each cylinder. Aside from that, the car is well maintained. I use synthetic oil, OEM Oil Filter, 300 Z fuel filter...

I cleaned the TB about 5K miles ago. The knock sensor was faulty and replaced recently. As of right now, the CEL is not lit. So why is my max trippin'? Anyone?

 

What kind of milage are you getting? Check your O2 sensors? Air filter? You're probably only about 10-15fwhp short of where you should be NA. Make sure you dont have any exhaust leaks? Belts tight? Flush fluids? Just some suggestions..

 

Well, gas mileage is great. I just made a 420 mile trip on tank full averaging about 80 mph. No 02 sensor problems (at least no CEL) , and the cone filter for my hybrid intake was replaced in Nov. Exhaust leaks, non that I know about.

That's about all I can say. I should be getting my clutch replaced sometime next month. I will replace the tranny fluid then.

What could be the problem?

 

Bump

 

I'm tellin ya, if you are Auto, you are maybe 5-10 off, and if you are 5spd you are 10-15 off. Some could be just dyno error (not all dynos read the same). Some of it could be correction factor (was the dyno at sea level, etc). Only other things to check would be... maybe.. cat clogged? All else fails, do an oil analysis.

 

Is this true? Where have you heard this?

 

I am a 5 speed, look at my sig. I explained that the first and second run (spraying) were done in third gear and the last run in 4th.

I dynoed with Carboy which is located on the South/East side of Houston. I assure that it is not more than 200 feet above sea level.

Well, I have never heard of this, but I'll be getting a full exhaust system soon. I'll be hollowing the cat or removing it entirely.

In addition, I'll see if I can get a compression test done this weekend.

Any other suggestions?

 

If all of your maintenance is done, have you thought about parasitic loss through the drivetrain? 155 fwhp would be an 18.5% loss from the 190 crank horsepower, which is I think towards the upper limit for the loss. A 5 speed should realistically have less than 15%, and an auto a little more. If you haven't changed your MT fluid in awhile, this may be some of the cause. It's worth a check.
As for a 65 shot giving you 90hp at the wheels, I can't totally explain that one. However, I wish I had mods that gave me extra hp over what they are supposed to. Could that be caused by jets, ECU programming, fuel pressure, etc...?

Dave

 

Dave, thanks for your response. And yes, my tranny fluid is the only thing that needs to be changed. I bought my car with 74,000 miles, and is now going on 101,000, I don't know if the previous owner changed the tranny oil. However, I will be upgrading my clutch soon, and of course replace the tranny fluid with either Royal Purple or Redline.


As far as JWT 65 shot giving me 90 to the wheels I don't know either, but I am not complaining. I don't have a Nitrous Oxide Pressure gauge, so I don't know the pressure when I dynoed. I do know however that it was full and pretty warm. I placed it in the tub with warm water for a while. I guess I must have been pushing 12 or 13 hundred psi. I was glad to see that my AF remained stoichiometric up until 6000. After that, I started going rich.

Hopefully, once my clutch and tranny fluid are replaced, I will see my missing 15 or 20 ponies.

 

Yes its true. Members have accidently used colder plugs when they dynoed NA and lost power. Some have claimed a loss of 20hp, which seems like a bit much to me, however lossing 5 to 10 wouldn't seem out of the question.