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I have been reading up a little on FI and it occurred to me that there ought to be some difference in the quality of Turbo vs SC boost. I’m just going throw out some assumptions that make sense to me and would love to get any feedback rooted in real experience and practice. Sorry of some of the questions are obvious but it can be a little tricky to find detailed information on this on the net, at least for me.

1.Well first of all SC would have nothing have no turbine in the flow of exhaust so one would expect backpressure on engine with turbo to be higher proportional to the amount of boost.

a. Does that mean that turbo engine will have slightly more trouble with scavenging exhaust from the cylinders thus leading to higher heat buildup and intake charge dilution?

b. Can SC engine be further enhanced by tuning the exhaust help scavenging via exhaust pulse timing (ugh, can’t remember the name of the effect)? If so, is this done and how significant are the gains?

2. Twin screw SC as well as rotos blower, at low boosts, are as or more efficient, in terms of adding heat to the charge, as turbo. However turbo is hooked up directly to the exhaust plumbing. Does the turbo efficiency rating take into account whatever heat seep you would get that fact or is it purely impeller efficiency rating?

3. It seems like it wouldn’t take a lot of tq to drive the compressor/blower so I would expect the ratio of tq to hp be higher on sc engine vs turbo engine while turbo would naturally have higher hp pound for pound of boost.

4. Specifically in RedShift SC thread it was mentioned at some point that it would be possible to control the boost per gear if real tuning options were available. While this can be done easily in turbo via waste gate manipulations how can this be done with SC particularly one placed after TB?

5. What ARE FI cams exactly? Do they just have more valve overlap to use the boost for a little blow through? If so are injectors usually tuned to fire with a little more delay after valve open to prevent blowing threw fuel?

6. This is a little general but with higher tq and hp output per rpm do oil/water/steering pumps become linearly better at doing their work or does it make sense to under drive them to the power level that they would see on a stock engine?

Are there any other differences in “quality” of SC vs Turbo boost or tuning directions taken with them? Thanks for any comments that will bring further insight!
 

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Ksan said:
4. Specifically in RedShift SC thread it was mentioned at some point that it would be possible to control the boost per gear if real tuning options were available. While this can be done easily in turbo via waste gate manipulations how can this be done with SC particularly one placed after TB?
you the only way to control the boost levels of a s/c is by pulley size, there is no way to really "limit" boost as there would be with a turbo.
 

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^^Acutally I have been testing out a way to absoutly do a boost by gear setup on superchagers, Should have it completed shortly ;) BUt if I tell you how my monoply on it will cease to exist sooo...your just gonna have to wait :p
 

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Highrev1 said:
^^Acutally I have been testing out a way to absoutly do a boost by gear setup. Should have it completed shortly ;)
this is for a supercharger correct???? could u PM me with the basics of how this could even be done i mean that is if u dont want to lea out your info.
 

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Yes supercharger applications, Say 5 psi in first, 7psi in second and full boost 3-6...Sorry can't give out any secrets on this one. :biggrin:
 

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Highrev1 said:
Yes supercharger applications, Say 5 psi in first, 7psi in second and full boost 3-6...Sorry can't give out any secrets on this one. :biggrin:
im gonna take a stab and say there has to be some sort of computer involved limiting the amount of boost coming into the motor, because the only way i know that a s/c/ can have different boost levels in to change out pullies.
 

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1. With a F/I its more important to just get the air out, not so much with the waves like in an N/A application. Most of the Non-custom Headers are limited to about 300 WHP or so then they become too restritive. THere are custom ones avaible for 300+WHP I ordered ONE

2. I think for turbos its Purely an impeller rating, although MOST are intercooled so IAT's can be kept to a min.

3. The laws of phisics can't be broken :D

4. I am not telling :p

5. Most F/I cams show little gains, 10-20 HP or so on the K-series. Also there have been issues with the stock chain tensioner with aftermarket cams.For now the best bet is an 06 TSX intake cam with a 02 RSX exhaust cam, from what I remember. There would be less blow by from the overlap

6. They are still spinning the same speeds, maybee slightly faster due to the increased RPM from the tunes usally so no real difference there.
 

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Highrev1 said:
NOPE...No computer.
ight now its just killing me to know because i know your not swapping pullies in between shifts....or are you.....do you have the little man from the star bursts comercial hiding in the engine bay with the tools to do a swap that fast????? lol but ill just be patient and wait to see what you have going on cause i truly am interested.
 

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Even some sort of stepper pulleys would work for it, think about it like a 10 speed Bike..I just thought of that one...BUT THATS NOT IT :p Its much simpler than that.
 

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Highrev1 said:
Even some sort of stepper pulleys would work for it, think about it like a 10 speed Bike..I just thought of that one...BUT THATS NOT IT :p Its much simpler than that.
which tells me more than likely i am over thinking this alot... damnit PM me lol
 

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i think greg is going for a series of pulleys inside eachother that will lock like the compressor clutch on the ac to smaller and smaller ones as you go up in gears. hope i didnt give it away.
 

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Highrev1 said:
NOPE :p Thats wayyyy too much work ;) I basically have it up and running for the RSX...hint hint
would gradually adding power through the gears help with the traction problem associated with FI Si's?
 

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Throttle modulation would be great if people knew how to drive and not spin tires, but most out there don't and need some sort of BBG.

Man a gearbox setup would be cool but big bucks I am talking relativly cheap here.
 

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Highrev1 said:
Throttle modulation would be great if people knew how to drive and not spin tires, but most out there don't and need some sort of BBG.

Man a gearbox setup would be cool but big bucks I am talking relativly cheap here.
Servo/solenoid valve using a restriction to limit boost? That's my guess :p
 

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the only thing with you "lie a bike" thing is most of the time when u go to a smaller pully after so much of a size change you need to go with a differnt sized belt, is this incorperated in your design or is there no need for that?
 
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