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How Much Boost Before Required Tune?

26K views 23 replies 11 participants last post by  Hojomama 
#1 ·
(Maybe turbo should be turned into "boosted" since some are experimenting with superchargers.)


Hey everybody! This is a two part question and I would like to tap the brilliant minds here on SCoA for information and help regarding my issues concerning that of which I am about to venture into.

Part 1

What would be a safe level to boost without tuning the ECU or changing anything? Would 3psi be too much? Would that be the safe maximum to start and drive around with for about a year?

The reason for the above question is because I will probably do this project in stages since my money situation is bad and I don't want to throw over $2k at the project immediately, but first put the supercharger, then with money, put more on and finish it down the road. Okay, back to questions.

How would I control the maximum amount of boost? Should I get a BOV to release anything above a certain PSI or should I get a different sized pulley?

Part 2

Where I can get good side pictures of the engine where I can see the view from the pulley side? I want to see how much room I have to work with here.

Where do you guys think I should mount the supercharger? In what location on the engine or next to what pulley?

Thank you guys! I can't wait to get started! :D

If you didn't see in my other thread, here are the pictures of this cutie and a video of it:


 
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#4 ·
I was recently digging down there to look at some options for my own project, and the AC compressor is real close to the fire wall. for intake plumbing, there is a lot going on behind the AC compressor- all the coolant lines are there, as well as the intake manifold. You may have to do some cutting and give the firewall a 'tubo bump' to shoehorn it in. There is about an inch clerance from the face of the pulleys to the plastic spash shield.
 
#5 ·
Excellent image Jwight! Thank you!

Paul, you are right. It is never, ever a good idea to start uncharted ventures without good funding. What I'll probably do is start up the project next summer, but get a Kuhl Fx body kit this summer depending on if I get a summer job or not. Right now, I'm just planning everything out so it goes as smooth and expected as possible. Next summer though if I have spending money, I'll stage the setup like I mentioned above and start out with a couple pounds of boost depending on the recommended feedback regarding that. What is your input regarding the low boost without a tune?

Gurps, thank you for your insight! It's highly appreciated! :D
 
#13 ·
A wastegate is an exhaust side component for a turbo - doesn't work for a supercharger.

Now I need to find some method or calculation or have one of our engineers hop on and give me insight as to how much the supercharger is going to take away by using the belt and then figuring out how much maximum horsepower I will be able to get with three pounds of boost at 5,800 RPM.
I don't know about how much power it would take off at the pulley, and of course there's all kinds of other factors to take into account here, but at the most basic level:

14.7 psi is atmospheric (what it's getting now)

+ 3 = 17.7 psi boosted

17.7/14.7 = about 20% extra power

70 HP * 1.2 = 84 HP

Looks like you're not getting much at 3 pounds...
 
#9 ·
Excellent insight Paul! I will probably keep the boost set at three psi and when I get the rest of the resources, I will add on to it. Coming to think about it, I probably won't get the body kit this year and save the money for the build next year when we can have some more spending money for unforeseen costs.

Now I need to find some method or calculation or have one of our engineers hop on and give me insight as to how much the supercharger is going to take away by using the belt and then figuring out how much maximum horsepower I will be able to get with three pounds of boost at 5,800 RPM.
 
#11 ·
Butch's response:

Brett it would have to be tuned no matter how much boost where to be run.., the other problem is it really needs an Intercooler to be Effective........., otherwise the increase in intake air temps would take away to much of the gain from the added boost...., and would also require to much timing retard to prevent detonation......, in the end without the Intercoooler the added boost at 3 lbs would not gain very much power to the wheels at all. If you noticed in the set up on the spitfire at 5 lbs of boost it only gained about 20 h.p. without having an intercooler..... and the engine was running Hot, because of the increased intake air temps.. At that low of a boost level brett (3) lbs the nitrous would give you a much better power increase for a lot less money.
Butch.
 
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