Beats me on the peak power thing, my stock engines with prochargers peaked well over 6000rpm and held on to 64-6500 without falling off as quick as Ed's. But if the boost is just hanging at 10psi at a certain rpm and not going up the power is going to drop like a stone after a certain point. On a centrifugal car the boost should keep rising even though you are well past the peak of the cam. The increasing boost will level the power off somewhat, thats why I could shift a z06 cam at 7000rpm and run pretty well with it

 

My friend was watching the boost gauge, it steadily climbed to 10# then held. Then barely hit 11# at the top of the run.

 

hey ed havent heard from you in awhile glad u finally got the D1 on,and kudos on the the nice area under the curve increase.sucks about the plenum blowing and lack of boost though.hope you get that figured out....question though.was this on race gas?the A/F ratio looking rather lean if im reading that right i see 12.3ish on parts????

 

There wont be a huge increase, I see maybe 1.5psi from 6000 to 7000rpm. It just doesnt make a lot of sense but ty-ty 13 is also peaking about the same with a simlar combo. Just fix everything and make a few passes, that 50hp across the board down low should make a pretty good difference, just experiment with different shift points and see what happens, dont get too hung up on the dyno numbers. Just remember with that 3.2 pully 6700rpm will max the D1 out.

 

Yes the increase in the curve is nice.

I did check some of my older dynos. And the peak moved to 5500 when I changed over to the 383. Before that, I was hitting peak HP at 6000. The stroke wouldn't change it that much?

No race gas. That was on 91. I was tuning with my wideband. AFR was 11.0-11.5 The dyno was about a point off.

 

I only mentioned that because of your previous post. I thought boost would always climb, just not power.

I don't think I will ever need to spin it to 6700 6000 outta do.

 

its a shot in the dark but its late and makes sense in my head....what if 1 of the 2 intercoolers arent flowing very well compared to the other one?would cause uneven pressures entering the plenum and might cause u blowing it up on only 10psi.
as far as the bigger stroke,adding those cubes from stock can make a bit of a difference its like with a turbo a T76 could make alot of hp cause it will be really efficient but on a 383 it wont make as much hp cause ur going out of the range after a certain point.generally speaking of course.

 

It should always climb until you get way past max impeller, its hard to look at the boost gauge and the tach and see how long its hanging though thats why its nice to log it. It should steadily rise with rpm though. I was at nearly 15psi with a 3.4 pulley at 6000rpm with the D1SC with a similar cam so thats a huge difference. 40 less cubes and little more compression but still 50% and turning the blower slower is a lot. Maybe its the FMIC making that big of a difference, kyle and jeremy (forcefed98) did the 3.5 intercooler to FMIC swap with a maxed out d1 so I would ask them what kind of boost difference they seen with the IC swap. I never ran more then a P1SC on the dual 3.5s.

I would still experiment with the shift points some, you might be surprised.

 

I am pretty sure my valve is too small now. There is too much boost when I let up on the throttle.

 

I guess it can be the small IC's. Just so frustrating that some have hit over 600 with a P1 and some hit 700 with a D1. Of course peak HP isn't everything. But something is making the power drop off, so there is something not quite right.

I am currently shifting @ 6400 so will drop that to about 6000 or so. Its better for the motor too.

I dont really want to go to a FMIC, but if that is the issue. I will. I would prefer the 4.5" coolers.

 

The 4.5 ICs would probably help, not saying to swap to a FMIC but I'd be curious to see what those guys were seeing with the d1s with the twin 3.5s when they were almost maxed out. Not to make you feel bad but I have hit over 750 through the TH400 and a D1 not really pushing it hard, so I agree something is up somewhere. Stevieturbo has trapped 148 or so with a 383 with a similar cam also I think so its not the engine combo unless its way off or its floating the valves or something..

 

welcome to my world of peaking before 6k rpms im not sure what the problem is with mine but maybe a larger blower will clear up the problems with these 4'' stroke motors... or maybe a huge cam... im not too concerned with it just yet b/c i've trapped 105 with it in the 1/8th soo far and really only made one full pass on MT dr's.... ill worry more about it this winter...

Tyler

 

That exact same blower did 580-630rwhp (with-without filter) on a mustang dyno on my car running on a stock engine with only a FM7 cam in it. I was running 3.85 pulley with the stock 3.5 intercoolers at the time seeing around 13psi. Im also using the SDCE setup. Peak TQ was around 4200 RPM while peak HP was around 6100 RPM. Maybe you need a slightly larger cam.

 

Thanks, now I feel real bad.

You have a dyno sheet on your car?

Maybe the belt is slipping alot with that 3.2 pulley. I guess I can try the 3.4 I have.

 

I found the sheet with the 50 shot. Running real lean.

 

i have one but no scanner... i could fax it to you on monday if you want it...

im convinced its the combonation of the heads and cam on my motor... i think the cam is too small and the heads are crapp (241)...

 

Can you send a pic? If not, a fax on mon will work.

I don't think its my heads. Maybe it is the cam or stroke
Green line is current. Red was my old 5.7L with a TR224 and the P1. Same heads

 

Kev it was a night and day difference between the FMIC and the crap ati twins.

I was stuck at 11.5's with a best of 120mph with the ati twin set up. 12psi with a 3.4 and it was all it would make with the twins boost wise. I did manage to go 11.36@120mph with a small 50 shot.

With the FMIC and no other changes except for a clean up on the tune due to seeing more boost.
11.10@125mph with the FMIC and the car was producing 15-16psi. It would have gone faster but I sold it to you shortly after I went to the FMIC to persue turbocharging.

The twins were very restrictive and my IAT's were outrageous up here where the air is thin. 160-170 deg temps were the norm on a pass. Plus loosing all that plumbing that the ATI set up had was worth something i'd figure.
J

 

[QUOTE=Ed Blown Vert]Can you send a pic? If not, a fax on mon will work.

I don't think its my heads. Maybe it is the cam or stroke
Green line is current. Red was my old 5.7L with a TR224 and the P1. Same heads

arent you on a 383 now... not a 347?

i believe kp said that a 4'' stroke will make it peak earlier with the same cam... wich makes since... i had a 236TR cam in my 346 and it peaked at about 6300 rpms... a guy from comp suggested a smaller cam and now i peak at about 5800 rpms.... i also gain 1 pound in boost from 5800 rpms to 6300 rpms but drop about 55rwhp... that makes me think its a combo of my crap stock heads and a small cam in a big motor (224/236 .601/602 114lsa)

whatever i decide to do next will be done through a knowledgable sponsor like dezracing since they do a sh*t load of procharger RACE cars... or brent@EPP...

i just have a feeling it will end up being a cam like 242/254....

 

that area under the curve pickup is sick!