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Old 10-10-2015, 09:13 PM   #1
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Supercharger engine setup

So I read this...
http://victorylibrary.com/supercharg...er-engine5.htm

Granted it's for bikes but I found this to be more in-depth than anything else I've stumbled upon; not to mention the displacement is more similar than the articles written around big block drag queens.

Figuring a modest 7-8 psi from the M90 Eaton mounted to the M20, here is the proposed plans I have for the motor. I would greatly appreciate some input as to where I can improve this design. So far, aside from custom pistons and Megasquirt, this is a relatively low budget build.

Ported 885 Head (ARP studs)
O-ring block
Valve Option A: 43mm (+1) intake with 38mm (+2) from a 2002 tii
Valve Option B: 42mm intake and 37mm (+1) exhaust
Stock 256 Camshaft
Stock Dual Springs
HD Rockers
85mm Custom 8.5:1 Forged Pistons
135mm B25 Rods
81mm B27 Crank
Megasquirt 2

Is there enough room to enlarge the exhaust seat far enough for Option A?

Am I missing anything or is there any reason to upgrade beyond this?

What size injectors do I need?

Is it worth replacing bearings, springs, pumps and all that to ensure longevity?

And lastly...
Power estimates? 250whp?

Experienced insight would be much appreciated as I want to have my setup as concrete as possible going into this build. I am ready to start gathering parts but I would like the advice only R3V can offer!
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Old 10-11-2015, 08:59 AM   #2
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I was using a centrifical so a bit different experience, I originally was going with a eaton M90(have a M62 and M90) but came across a Paxton centrifical so ended up starting that. It was an experiment so started with a stock b25 with a SETA cam with dual springs, It was still running stock headgasket and stock head bolts, 2+ years and learning to tune MS and no issues. For the next one with a centrifugal SC(I have a vortech to use now) I will use a bigger cam.

My opinions

* Porting is not needed
* o-ring block is not needed
* Bigger intake is not needed for a boosted application at your power goal
* the exhaust valve is already biased on the large size but not as much as they are stating
* A +1 valve is an easy add as you can use the stock valve seat, a +2 would probably need a seat change
* 8.5 is way too low of compression for low boost supercharged application, I would be looking for ~9-9.5 myself
* With the prices of 84mm+ cranks now I would stroke it especially if you are going lower compression to make up for torque loss
* Running at 8-10psi a 250whp goal is an easy target
* you will need a stronger clutch, the stock one starts giving out at that HP(torque)

I would use 42lbs injectors(you can get away with ~30 for your intended goal), that will give you head room on your goals and if you decide move to a turbo which most that start on an SC setup goto after a while 8^)

My opinion is build the SC setup on what you are currently running, gather tuning experience and mistakes with MS and then conclude your SC setup is worthy (and not give in to the dark side and go turbo, boost is addicting) then look to building a boost specific engine.

I think you will find the stock motor will be a great start and a little boost really wakes them up, I think the 84x84 econ stroker build would be a great build to use
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Old 10-12-2015, 06:34 AM   #3
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Thanks whodwho! So 42# injectors and a clutch. That's what I needed to know.

I based the larger intake off of the ratio mentioned on that link. It's more of a relative thing when going for +2 exhaust valves. Is there really enough room for another 3mm of valve in each cylinder? That makes me very excited!

Currently I am running an eta so that's why I'm doing the baby stroker. Seems like a waste to blow on an eta, lol. Also i have 2 other b27's laying around so I couldn't justify more stroke (going with what I've got).

As far as the power goals, i was trying to be conservative. I would love to pull 350hp out of her if it's reasonably attainable with this setup. I'm still wrapping my head around how much boost a roots can deliver, effective compression ratios, etc... and on another note, I'm trying to avoid running alcohol injection if possible so this is intended to be a pump gas build. I would consider e85 if i need more detonation protection.

And last but not least.... f*** turboz! It's all about the linear delivery in my book. I'm not a drag queen so as long as I can surprise some people on the streets I'll be happy.
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Old 10-15-2015, 08:08 PM   #4
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So I've been looking more into cams based on the desired traits listed in that link and others and I'm finding that:

-Minimize overlap
-Less duration is needed
-With no need for duration it becomes more advantageous to have a later exhaust opening to prevent bleeding off your power stroke and also an earlier intake closing to increase compression as well as avoiding screwing with intake pulses and backflow bs

.....SO!


How 'bout that eta cam in the 885 head? I know the bearings are different but it has more lift, with less duration and the least amount of overlap of any cam i've come across. It seems to be the ideal choice. Can it be done?? If not, and I was determined to make it happen, how could I MAKE it work?
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Old 10-15-2015, 09:14 PM   #5
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That's why I was running it, an ETA cam in a 885 head is what is in a SETA engine. There is a 4 journal and a 7 journal version of the cam so you should be able to find a 7 journal cam.
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Old 10-15-2015, 09:36 PM   #6
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Outstanding.
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Old 10-15-2015, 09:38 PM   #7
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Looking forward to what you come up with. 8^)
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Old 10-19-2015, 05:55 AM   #8
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Somebody was just telling me they ran a m90 and had to pull through the throttle body to avoid boost spikes when it opens. This would put my throttle between the air filter and the blower then sending it pretty much unregulated into the cylinders... This seems like total bologna from where I'm sitting... Can anyone confirm this?
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Old 10-19-2015, 06:43 AM   #9
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No air in no air out - this is a common setup and I believe how they ran stock, it also helps cut down the blower noise.

Are you running the tbird one or one from a GM? The GM ones have built in bypass built into them, the tbird one doesn't. You will want to run some kind of bypass to help transition from idle/off idle
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Old 10-19-2015, 10:27 AM   #10
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I'm running the GM one. Nice to know I don't need to run a bypass. So I should put the throttle before the blower then? Hmm seems so weird.
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Old 10-19-2015, 03:54 PM   #11
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I have the throttle before the blower and it's lovely. Have you read my (extremely long) original build thread? It's a lot of crap, but a lot of good trial and error too.
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Old 10-20-2015, 09:51 AM   #12
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BlowA

Quote:
Originally Posted by Meta View Post
I'm running the GM one. Nice to know I don't need to run a bypass. So I should put the throttle before the blower then? Hmm seems so weird.
I have an Eaton-M90 on my E30-M50 car - Throttle body needs to be before the blower with any type of roots blower & you absolutly need a bypass - I have two of them 1.0" ID and coupl use probably one more when I up the boost.
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Old 10-20-2015, 10:52 AM   #13
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I have read the majority of your thread ether-d.. You're my low budget superhero lol. I still need to read yours though lithium. A built in bypass seemed like it might have been a little overmatched so it's good to know multiples can be used. I've heard a roots blower doesn't make actual boost because it doesn't compress the air. Is it possible to get higher boost out of the m90 with a pulley change? I would love to push output into the 350whp range if it's practical
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Old 10-20-2015, 10:55 AM   #14
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I think about 12-15 psi should do the trick...
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Old 10-20-2015, 03:19 PM   #15
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Here are a few links that helped me make decisions.
I doubt an M90 will pump much more than about 11or12 PSI unless it's ported etc...
My guess is 280/290HP - but amazing torque & throttle response.
I haven't had my car on a dyno yet / but when the pedal hits the floor the boost is instant & so much fun.

The Jegs article is really well done.

http://www.mscperformance.com/specpg2.html
http://zzperformance.com/3800/pulley...-system-1.html
http://www.culvermotor.com/Engineeri...alculator.html
http://rivperformance.editboard.com/...ercharger-info
http://www.jegs.com/s/tech-articles/...+-+Centrifugal
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