Here is a comparison of the difference in powercurve between the MD and dynojet dynos: The blue lines are the MD.
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400 RWHP NA build
- Thread starter poisoned apple
- Start date
i saw you say one time that you seen a car equipped with an fr500 intake manifold gain ~25rwhp with the intake lid removed. wouldn't adding spacers unshroud the runner inlets? also with the bottom half cut off the fr, i'd imagine it's starving for plenum volume at 8000rpm.
Mihovetz did a test where he removed the lid and the power did increase, but for some reason a large spacer does nothing. Brandon Alsept put a thick spacer on his NMRA Pure Street car and gained nothing, this engine was over 500rwhp at the wheels and spinning over 8k.
The fact that this engine has not even peaked yet hasn't revealed what it will do @8k. It makes peak at 7500-7600 and carried to 8k with the stock TB. The longer it can hold it up there at peak and make a few more is what the goal is. Not being able to turn it tight is the biggest issue right now. Whenever he's ready to put a PCM in the car, that's when we can figure that out.
Aslept's engine is completely different than zacks. Aslept's is a class car with many restrictions that severely effect the way intakes and induction works. Race gas, class limited is a different than a pump gas street engine. That engine needs a larger tb am more plenum. But we will see when it gets "turnt up". Just gotta try stuff.
Car sounds pretty awesome btw!
Car sounds pretty awesome btw!
Does Brandon's need less air...no. I have a graph for it somewhere.
I would think a road race would not want a more broad powerband.
"Turn it tight"?
I would think a road race would not want a more broad powerband.
"Turn it tight"?
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I'm not saying it needs less air. I'm saying a cam limited motor does weird stuff to the harmonics. You try an turn a bunch of rpm with it but the lift rules it makes it difficult. As far as road race engines yes, you do need a somewhat decent power band. It has to come off of corners and also needs to make power past peak.
"Turn it tight" means more rpm.
"Turn it tight" means more rpm.
The difference in power/cfm requirements is very little on a 4v when the lift difference is only .050-.075". In fact, I've seen little to no gain when going from .425" to .475". The curtain area is so great that lift matters little.
I'd advance the intake cams a little to broaden the powerband, rather than spinning it higher, but that's me.
There are 4v cams that run in American Iron SCCA that run .585-.625+ lift. I'd put as much lift in the car as I could if rules permitted for a class engine. If a pure road race car, no street driving, I would put the highest lift cam that would fit, but the maintenance required between races isn't practical for someone who plans to drive it around not on a road course.
03/04 heads cannot run lifts that high without longer valves and expensive spring packages. However, those with GT/GT500 heads can and will gain some as a result but even Roush prototype cars ran lifts only in the .475-.500 range.
Take a look at the lifts used in the top 2 engines in the 2013 Engine Masters Competition, both had over 400ci and ran GT500 heads, one ran .625 lift while the other was under .500. The power differential was minimal and the only reason the higher lift engine won was because of injector placement and headers which allowed for more power down low. One would imagine with $60k at stake they would use lift amounts that would maximize power.
You cannot compare the engine masters engines to race engines or road race for that matter. You are talking about an engine that needs to peak around 6k and have wide power band. The emc engines have an rpm limit which is below the peak of any road race modulars. Two completely different world's
Oh yes I can compare the two as higher lift adds power everywhere in the powerband unlike duration. Of course the additional power offered by higher lifts will only be realized if the heads need it (higher lift) to produce more power. In the case of the 4V it's just not needed.
The higher lift MH and MHS lobes from Comp (for the GT/GT500), .585" and .625" are great and offer some seriously quick ramps, they are also very stable at high RPMS but also noisy due the valves slamming shut.
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Valves slamming shut is not stability. As you increase in rpm lift becomes more paramount. As velocity increases with piston speed it's important to get the valve out of the way to prevent turbulence. 4v heads already have very high velocities for the csa of the valve and size of the port. Turbulence kills power past peak almost as bad as valvetrain issues do. Yes you may have not noticed anything at emc but what was the piston speed at peak torque and at peak hp? Also what was the average csa of the head?
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How can you say you would advance it if you don't even know where it's installed at?
I don't need to know where it is to recommend advancing it, one look at the graph is all that's needed.
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I did not say that slamming the valve shut was stable. However, Comp says the MH and MHS lobes are more stable at higher rpms than their standard lobes.
I understand what you're saying, but what works doesn't always agree with theory.
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You can only advance then so much. How do you know they are not already advanced?
Knowing where they are at currently isn't needed? They are in @ 113, as tight as I could get them with adequate clearance. If I could have got them to 112, that's where they'd be.
That LC is too high for an FR500 intake and a stock stroke/bore engine. I had the concern that they were too long when he posted the specs. Did he or whoever ordered the cams tell Comp that the pistons had no reliefs?
Listen, this engine makes great peak power for a pump gas combo and kudos to all involved.
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You don't even know where the cam is, all he gave was the lsa. Where is the intake centerline? Where is the ivo/ivc points? You can say what you would or wouldn't do but it means nothing if you don't know where you are starting.
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