I've been looking at some cams, but figured you guys would probably know the best one to get. Going to be turboing (pretty sure twin for those of you that care) soon, but want to do a cam swap first. Anybody have any look with some good cheap ones? I can tune the ECU too so I'm not really concerned about that. Thanks!

 

gm 94666492

 

Why is your focus on cheap if you are going Twin Turbo?
Little known secret, forced induction helps the TPI breath up top and extend the RPM range.

Personally I think you should be looking into something in the 218/224 with a 114 LSA for a turbo.

 

Watch Richard Holdners TPI Turbo video. The power curve of TPI is exactly the same with boost as it is NA.

 

i know that's not true at all. My car doesn't give it up at 4600RPMs anymore.

 

Not true.

^True^

You likely made other changes that affected the SHAPE and/or the location of the peaks, of the power curve. Have you seen the dyno graphs of STOCK L98's with a turbo kit installed? Or '80's Callaway TT Corvettes? Same peak points for both tq and hp...just moved way, WAY up the scale. Have you seen THIS RECENT THREAD on the 'Vette forums? Guy added a turbo to his L98 and made 362/556 WH/T at 3800 and 2900 respectively. I don't see how the turbo extended his RPM at all. By 5000 RPM, it's down to ~300 RWT.

 

Not really, but I don't see how forced induction shoving air in isn't changing the runner dynamics.

My car is on factory heads/cam and replacement injectors... it is running a 3.45 9-Bolt for what that is worth. Headers and supercharger are the only changes... If it still peaks in the same place, the drop off is noticeably different. I was actually talking about this with one of the guys in the Corvette club the other day. My Iroc and my borhters 88 Corvette feel very different to drive. Still feels like his has more low end grunt than mine even though I have a SC. I was theorizing that the added drag ate up some low end torque and made up for it when the boost started to build and carry past that 4600RPM wall.

I actually stated once I am happy with my EBL tune I would like to get it on the dyno and see what the graph looks like. Just not peak to peak, but how do the curves differentiate because it sure feels different.

 

It does....but not in a meaningful way.



Well...that is likely what you need to do. We know that SOTP don't mean ****. I'm sure the car makes great noises and "feels" fast above 4500....but is it really? You don't know. We don't know. You need a dyno session or a drag track day experimenting w/shift points to suss that out. Also, it's possible that the way your centrifugal charger is driven, you're boost curve is skewed "up high" and that it could cause a lack of low end tq and push the power up high...but that would be an inefficient, un-optimized set up.

If you look at HP graphs of boosted L98's they pretty much make the same shaped curve at the same RPM...just more of it. :thumbs:

 

When the mention of engine components combined with the word 'cheap' is mentioned, my first thought is anything made by Dorman.

Better you than me though.

 

Even more of a reason to invest in a decent cam. If I was tearing in to my motor, I would definitely look at something to lift the RPM range and hold the exhaust open a bit longer. I still think the charger will overcome some of the limitation of the intake, just may take a cam to take advantage of it. I don't think putting a charger on it all of the sudden makes it a 6K RPM engine, but I think you should be able to get it to flow to 5500 with the right Cam.

 

Agreed. FYI, here is a dyno run of an '89 Callaway TT; note the peak/RPM's

 

Boost can over come a na motors past peak rpm potential.

power curve can follow the boost control

if you took a Tpi motor that peaks at 4200 and falls way off at 5000, i could make it peak at 5000 by adjusting the Boost curve shape by applying more boost at 5000 than at 4200

think how a centrifugal blower works. Boost by rpm. If it makes 12 psi at 5000 and only 8 at 4200, it will show peak power by 5000

if you apply a flat 12 psi across the board, the power curve will be like the na curve, for the most part

 

I am a centrifugal, but I don't have anything recording my boost profile yet.