So, I am interested on getting some feedback on my HP and TQ of my new 383 - 6lbs of boost - see sig for other details.

I dyno'd it last week and was pretty happy with the peak results.

I posted them on another site and had a member comment on the fact that my TQ was really falling off at upper RPMs.

So I looked at the curves of my old 350 with 6lbs vs my new 383 with 6 lbs - (yes, i changed pulleys to get same boost with bigger motor)

Basically, entire short block is new (including cam - Comp Cams 576/570, 230/236, 113 lsa)

Intake, heads are exactly the same - untouched.

It is interesting to me that the slopes of the curves after 5k RPM in each motor are very similar - should they be?? -I would think that the cam would have significantly changed that. - maybe this is stupid....but it did make me wonder.........

I had run some simulations on engine analyzer pro before I built this motor and differences in valve sizes really did not seem to make much difference with the other characteristics of the stock heads....but.....maybe it was wrong.....

Ideally I would like my horsepower to peak at about 500 at ~6200rpm and I would like my torque to be 425-475 in the 4000 + range -- in other words, I would like less slope on my TQ line and a little more slope/peak on my HP line.....

So, what do you think is causing this and what do you suggest I do next (cheapest route is always best...)

My supercharger is maxed out......600B......I can not put smaller pulley on it (procharger does not sell one).

Intake - can I really do much with another intake
Heads - if so, which ones?
New Super Charger - this block could handle a lot more boost - F1? D1?
Cam(I don't think this is it....but interested in opinions)


http://s252.photobucket.com/albums/h...0vs383dyno.jpg

http://i252.photobucket.com/albums/h...0vs383dyno.jpg

 

Pulley up, bigger injectors and retune.

 

sorry - should have said i am already running the smallest pulley i can for my 600B - 2.65 - procharger does not sell a smaller one and says i will over spin my supercharger if I get a custom one made - plus belt slippage issues.

i updated my original post.

 

How much timing are you pulling with your MSD box? How much timing are you running in the 100KPA area of your pcm timing tables. Also, what intercooler are you running?

 

I am not a supercharger guy, but my first thought is the supercharger is maxed out. That would explain a lower peak rpm and dropping afterwards.

Of course a million other things could do that too.

 

I am only pulling 1/2 degree per 1lb of boost.

At 100KPA I am running 30.5 degrees total timing from 4000rpm plus. With 1/2 on the msd box I started seeing detonation/retard at anything above 31 degrees on the dyno last week. -- so at 6lbs of boost at 5-6k rpm I am running ~27.5 degrees of timing. The motor was built at 9.5.1 compression.

I am running the stock procharger single intercooler that cam with the 600b kit. It sucks, but is better than nothing. I have mounted an axillary fan on top of it to try and cool things down.

 

How big is your crank pulley?

Assuming a 6" diameter crank pulley and 2.65" blower pulley, you're only spinning the impeller at 41,433 rpm at 6,000 rpm. P600B only has a 3.05 step up ratio.

According to the procharger specs, the max impeller speed is 60,000 rpm. From the specs, you're a long ways from maxing the blower.

http://www.procharger.com/models.shtml

You would need an 8.75" crank pulley to get 60,000 rpm at the impeller at 6,000 rpm with the 2.65" blower pulley.

A 7" crank would put you at 48,339. This may be close to the practical limit.

I see there is a 7.65" crank pulley available, that would be 52,828 rpm which is getting up there. I also found a 6.45", so it all depends on what you have. If you already have a 7.65", I agree you may not want to spin it much faster.

This list shows a 2.55" blower pulley which would put you around 55,000 rpm with a 7.65" crank pulley:

http://www.exoticperformanceplus.com...html?item=1042

I don't know if it will really live at these speeds, Vortech's are said to be good to 50k.

I've also read that those intercoolers result in boost drop of about 3 psi. Procharger used to advertise this and set up their kits to deliver 3psi above the rated boost (pre-intercooler) to compensate. Is the denser charge and extra spark that you can run worth 3 lbs. of boost? Maybe not.

I suspect that the intercooler is the limitation.

 

Yes, the intercooler is the main problem. I would ditch that intercooler all together. It is doing absolutely nothing for your IAT's and restricting your intake. Just run the pressure pipe straight from the blower to the intake elbow. Then call up Alkycontrol.com and get you a methanol kit(This will help supplement your 42 pd injectors). You will gain 4 psi and your IAT's will drop 60 degrees. Then watch that car come alive!

Also I would recommend putting the stock timing tables back in and pulling 1.5 degrees per pound of boost with your MSD BTM. Make sure your AFR is pretty close to 11.8. It will make a big difference.

 

with the guy above. Intercooler.

 

or ditch the intercooler for a bigger one and run new piping.

 

Odd, had my car dynoed in 04 and had similar results. I had stock heads and intake a cc305 cam and a 2 core intercooler. I was making 10pounds of boost with a P1sc. The guys at the dyno felt that the trans was not holding up to the power of the motor past 5000rpms. I was and currently still running and a4 too. At that time I had a 2600rmp vig converter in the car.

http://memimage.cardomain.net/member...29_77_full.jpg

My timing was some what low too. I was running 23 degrees of timing. After the dyno run above we had some issues with my trans and also some clamps on the pressure side gave way so I pulled it off the dyno. Brian at PCM for less was there tuning my car and also said the car was also getting some false knock and I should benefit for another 3 degrees of timing. I wanted to be on the safe side.

I moved from NJ to FL that year and pulled the blower belt off the car. I am only now getting back to the car thing and hope to have it running strong later this year.

Please let me know you find out and I'll do the same if any changes I make affect the outcome.

Thx,
Claude