I have been searching for a proper set of cams lately for my future supercharger. I came up with this question. Performance cams are built with different duration and lift so that the intake cycle and exhaust cycle overlaps each other. By leaving the intake valve open longer, the air and fuel continues to force itself into the cylinder as the piston starts its compression stroke, exhaust cycle. Helping the N/A cars getting better air flow in and out of the engine. But with the F/I cars, would it be as efficient as the N/A? As the F/I forcing a lot more pressure into the engine to create boost, wouldn’t the exhaust overlap let out the pressure from the intake that results in loosing pressure? Or cams will only work with Turbo instead of Supercharger because the fact that turbo boost is driven by exhaust stream compare to supercharger by the crank?
Not saying N/A cams do nothing for the F/I motors, but how well will it do? Will the abilities of the F/I suffer because of the cam?

Are N/A cams useless to supercharged motors?

 

Less or no Overlap is ideal for a FI motor. Just check the cam sheets.

 

Right now the only solution that I can think of is to get the Nismo camshaft blanks and have them custom ground by a place like Comp Cams or Crane.

 

Tomei's would work great

 

JWt's would work better..less valve overlap

 

Can you use cam gears to dial out the overlap?

 

The Tomei 256 cams would be a great option for FI. They still have increased lift but not as much duration as some of the cams more suited for N/A setups.

 

Based on a couple of books I've read on the subject, it is VERY difficult to significantly improve your cams from stock when you go F/I. Even if a small gain is achievable, cams are expensive, and labor costs are high as well...so they may not be worth the money.


That said, the only cam I would go with is the JWT...but again..I'd only get it if it was free...they are soooo damn expensive, and labor is outrageous too.

 

Exactly what I was thinking.

I wasnt trying to find out which one works best or better. Better does not mean good. Its just a compareson. 5 hp gain is better than 3 hp gain. But 5 hp gain may not be good.

I was trying to find out how well would it do on F/I motors. For example, JWT claims to gain 15+hp to N/A motors. Plus exhaust and intake mods, it should gain at least another 15+hp. So 30+hp is nice to have for a N/A. But as for a F/I, would it even gain more than 10 hp consider that air is already been "Forced" into the cylinders. And as the exhaust valve overlaps, it releases its "forced" intake energy. Taking out the meaning of a forced induction/boost pressure. I would spend $1500 for a mod thats got the potential of making at least 30+ gain over the current status. But only for a couple of more hp for a F/I? I may have to think twice.

So far I have not seen any F/I Zs with cams mod. Is there one?

 

Which ones? I believe there are 3 different specs they make.

 

 

It is expensive and given the potential increase, it probably is not worth the money, but you will see an increase. Mcduck has the nismo cams on his SC'd car for a reference. He is making a fair amount more HP then many others with the Vortec setup. Cams and Crawford headers probably contributing a fair amount to those results.

 

I see. For the money, I would assume exhaust mods are far more ideal than cams then.

Thanks all for the replies.

 

What zzzya said...

Based on what I've seen posted here, the biggest difference between my Z and others with Vortechs are the Nismo cams and the Crawford Headers. Some Vortech 350Zs have the some or all of the other mods I have.

It seems the average for a slightly modded Z (exhaust and plenum upgrades) with a Vortech is around 380rwhp. With Nismo cams & Crawford headers, I'm hitting 420-425rwhp. So, under FI application, those two mods are netting me about 40 peak horsepower. It makes sense, tho... both of those mods are freeing up the engine's breathing cycle. So, the additional air/fuel being pushed into the motor has more room to get out after ignition.

Had the JWT cams been available when I did that mod, I probably would have bought them instead, but I'm very happy with the Nismo cams under FI.

Good Luck on your project, Phat! Keep us posted on your progress and results.

 

cams could be cost effective if you do them while improving the rest of your valve train or rebuilding your motor. i just could not imagine installing them alone.

how much are they for install 1200-1400? plus parts.

 

I have the Tomei 264 cams and at 10psi my car dynoed at 452rwhp and 417rwtq with 8.5:1 compression pistons. If i remember correctly skiddazles car made almost the same horsepower at 10.5psi with stock compression. I thought that my car would put down a little less than his considering that i had less compression and i think whats making up for the loss is the cams, its definately not the exhaust because we have the same cat-back and i don't even have a y-pipe, mine is stock.

 

Interesting. How is the idle on the Nismo cam if you dont mind me asking?

It now comes more clearly to me that although cams would make still a difference. But only will produce more sufficient AFTER most of the intake/exhaust modifications. It certainly will not be the top of my list, but it shall be on the final stages.

Yes, I agree. Would make sense to get cams with pistons/rods. Labor is about $800!! the last time I checked.

Stock is 11:1? I know lowering the compression prevents the engine to pop during high boosting. But what other effects does it do?

 

Actually stock compression is 10.3:1. Lowering compression has no other effects besides what you referred to as popping. It basically allows for higher boosting. But i think you missed what i was trying to imply, what i meant was i think my cams made up for the loss in compression in the comparison above.

 

My view on this whole thing is that you want to eliminate overlap to keep the boost from blowing the intake charge right out the exhaust valve. You can increase lift to get more air in at high RPM and that will also help if you raise your redline. More duration makes more power as well, but you lose some idle quality.

 

Yeah kudos , I got ya. Thanks.

More duration means more overlap no?