F.A.S.T. 102mm LSXR or GMPP single plane
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I think a lot of it has to do with the cam shaft. More info is needed.
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Camshaft is definitely going to determine the power output. The single plane is going to make more power at a higher RPM than the FAST will. For a nitrous app I would think the single plane would still work best for distribution and ease of nitrous option's with large shots. A plate is easily able to spray up to 4-500hp worth of nitrous without needing to be direct port. For larger shot's I would go with a single plane before a FAST. They seem to handle nitrous backfires better too! haha
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251/259 .661/.664
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quoted for troof.
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Even on a 100% track car? Have you seen this first hand?
I have the FAST 102mm on my car and it makes great mid range power all the way till I shift at 7000. I cant feel a fall off. Ive owned Victor jrs and even a BECK manifold before and this on seems to make the car much more responsive and more broad power band. I dont dyno my cars so I dont have any sheets BTW.
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We've done back to back testing on an engine dyno of a sheetmetal, single plane and FAST 90 on a 422 LSX w/ TFS 245's at 13.5:1 compression. The FAST crushed the sheetmetal and beat the single plain until it peaked around 6600. The single plain and the FAST hung close for another 200 rpm or so IIRC, and then kept on pulling to peak in the 7600 area. Sheetmetal just seemed to keep wanting more RPM. I would think that the 102 would have performed better on this big inch motor but at the time, it din't exist.
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That cam isn't really gonna work well on a single plane I don't think. It would work better on a fast intake I would think. Nitrous was the deciding factor for me. A single plane on the jug works. Nitrous on a FAST bigger than a 150 hit would 'need' to be direct port.
I agrees that the fast will make more power everywhere up to 6k but in a nitrous app I'll take a single plane anyday over the FAST.
My 403 lost no torque or midrange going from a FAST90/cam combo to a ported Vic Jr/cam combo and made more power from 4500+ and didn't fall of like the FAST did either!
Different setups will like different things. I'll go ahead and say that a 251 on the intake side is gonna kill some midrange no matter the manifold aspecially if this is going on a smaller cube motor.
I agrees that the fast will make more power everywhere up to 6k but in a nitrous app I'll take a single plane anyday over the FAST.
My 403 lost no torque or midrange going from a FAST90/cam combo to a ported Vic Jr/cam combo and made more power from 4500+ and didn't fall of like the FAST did either!
Different setups will like different things. I'll go ahead and say that a 251 on the intake side is gonna kill some midrange no matter the manifold aspecially if this is going on a smaller cube motor.
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Theyd start to separate around mid 6000 rpm. If 7K is all you want... well Id say thats your answer
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^^^ what he said^^^
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I'd like to ask a slightly generalized question. So I've seen where a blower added to a combo can shift up the power band 500 rpms and more. I remember one time about 7 years ago talking to Jay Billingsley about nitrous and he said something about how nitrous can bring the power band down... Can anyone take my comments and react (constructively of course). I mean I know you'll want to spin a Briggs max N20 engine up there because those 4xx cid engines are SR and built to run at 8500 rpms etc, rpm makes power for NA. How does nitrous change the power band?
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If you take an NA engine that peaks at say 7000 rpm, and the exh lobe system etc is sufficient enough to blown down its 700 hp in the time given, stuff another 250 hp worth of combustibles in the chamber, what happens to the mass of spent gases? It goes up quite a bit, and you have same time to empty mo chit. Pumping losses go up.
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Supercharged stuff can do the opposite because your cam timing may be sufficient enough to fill the cylinder to a xxx rpm, but with the manifold pressure it may be able to successfully fill the cylinder till a later rpm. Exh will take more to blow down also, but most supercharged plain jane stuff already crutches the exh lobe, and the change in cyl filling outpaces it. Alot of plain jane nitrous guys take their NA setups and strap a kit on it so it will be more pronounced as the exh end hurting it, if cammed correctly, it wouldnt change at all. Do what you need to do with the valve timing so the motor is happy where the intake manifold and cylinder head are best suited and its all irrelevant
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There are alot more knowledgeable guy's on this forum than I on this subject but I believe the reason nitrous 'seems' to lower the powerband is because of the cylinder pressures enduced at lower RPM. Think about a 250 shot. It's adding enough oxygen to generate an extra 250hp. So at lower RPM there is more nitrous entering each cycle/second than at a higher RPM because your still spraying in the same amount of nitrous no matter what RPM your at. That added nitrous per cycle creates much much higher cylinder pressures. This is why nitrous car's generate such high TQ numbers lower in the RPM.
Usually blower and turbo applications don't have this affect because they arent generating the equivalent airflow at low RPM as they are in the upper RPM's. This is why boost is usually linear power vs low peaky power of nitrous.
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