Supercharger throttle body placement question

**Xnke** · 03-09-2017

I've taco'ed a throttle plate with the M62 on mine, it was not fun.

Suck through throttles or dual throttles-blow through throttle with a PD supercharger with no bypass valve is dangers. Regardless, you MUST MUST MUST use a compressor bypass valve with any Eaton blower! Not bypassing the blower at idle and low load will result in the blower overheating and seizing solid. Leave the blower unbypassed at idle for five minutes-it'll lock up solid from the heat. Never mind the stop-and-go of traffic...that'll lock it up even faster!

I have two seperate throttle cables operating two throttle bodies-a 60mm on the intake plenum, and an 88mm on the inlet of the supercharger. I modified the inlet of the M90 case to allow the full 88mm throttle. The quadrant arms are different sizes on the two throttle bodies, so I had to make matching quadrant arms to make sure the two throttles opened at the same rate as I pushed the throttle pedal.

You should be able to mount the blower anywhere you want-but the merc blowers are not what you want to base your design on. That clutched pulley wears out and won't engage, and if you're like 99% of all the people who want to use it specifically for that, I've got news for ya-no mad max style blower engagements. It'll immediately burn up the clutch and will never work properly again after that. The blower is normally held engaged by the computer, and the computer DISENGAGES it over a few thousand RPM-it's only working for idle-3000-3500RPM and then the computer drops it out and bypasses it. Also, it's very expensive to get an interchangable or any other size pulley for the blower...500$ plus last I checked into it. No other systems will fit it directly.

Also, the blower doesn't have to align with the intake. You can cut and fab a new plenum to mount the blower, and put it anywhere you please to get the belt lined up, from what I remember the intake side of a quad-4 has lots of room under the intake manifold.

**BigBanks78** · 03-11-2017

I read most of ur reply but not much time at moment but wanted to show u drawing and see if u thought it would work. I just changed starter and there isn't room under intake without moving alternated or a/c. In a Fiero there's even less room there plus stock belt is to narrow and not enough room to push beyond the harmonic balencer. I have a 2 to 1 pulley drive. Not going to use clutch, gonna lock it. I have a 13 inch lathe but haven't tried to make a pulley yet.
I'll reply after a bit with more.

Ok can I sync 2 TB's in this way and it work, sync one to the mainTB to close NA filter as main TB opens. #1 on drawing closes as #2 opens. And what about running air from after the inter cooler back thru SC when not in use?? Yes I'm gonna use all the safety stuff/valvesimage.jpg

**BigBanks78** · 03-12-2017

Ok is the throttle body on SC to slow down the air when you let off throttle? Where did route your bypass valve to/from? I readthat if you recirculate the air back thru SC that it would help keep it cool when not in use. This is my first boosted build so I'm sure I'm not familiar with all my options for boost control and configurations. I tried to google for diagrams but didn't find much variety. But I'll look up the setup you are talkin about.

**Xnke** · 03-14-2017

The supercharger inlet needs to be throttled for both noise (Don't even argue this, it's so loud you won't want to drive the car...130dB+!) and to remove the 45 horsepower load on the engine from running the supercharger at full VE. The bypass is not needed to prevent throttle plate damage-it's to prevent the blower overheating when you have the inlet throttle closed. A positive displacement blower with a closed throttle will try to pump that 20kpA vacuum behind the throttle down to -60kpA, and it will fail to do so! But, that won't stop it from trying and it will get VERY hot as it attempts to do this. Hot enough to cause the rotors to rub and sieze in the case-so you need to have the bypass valve unload the compressor.

**BigBanks78** · 03-16-2017

I will b using a bypass valve, when I say recirc valve or BOV I mean bypass valve but I was thinking the bypass valve would do double duty, release pressure when over boosting and bypass SC when not using. I can get an external valve like that right? If so can do you mind giving me some good terminology to search and some specs to go by? I see BOV's on web, some look like they have a 1/8" vac hose nipple on both sides of the diaphram but they don't have image.jpgmuch of an explanation to wether they can b controlled both ways. I already have a bypass valve control solenoid off a Buick 3800. I get it about noise. I watched youtube video of a vw with this SC, bov vented to atmosphere and I can't do that loud PPSSSSSSTT every time I shift so was going to vent mine back to inlet. I will put TB on inlet no argument :-).....do I route bypass behind sc tb? What would be a minimum tube ID for bypass tubing? Will the engine pull a vacuum if through SC TB when SC is bypassed, I mean using the SC TB as only air inlet in the system? I should be able to control the bypass valve in all ways with the 749 right? With the wastegate control pids....

**Xnke** · 03-17-2017

You need the one sold specifically for supercharger use-the poppet type do not flow enough to be useful in a compressor bypass valve.

The one from the Mini Cooper S would work just fine:

http://www.ebay.com/itm/Mini-Cooper-...-/191986610258
http://www.ebay.com/itm/2002-2006-Mi...-/262896611747

You might look at the stock eaton blowers on Ford and GM stuff for your ideas on where and how to plumb it.

**BigBanks78** · 03-17-2017

Ok GREAT :-) Thank you!! I'll head out to a pull your own part yard and c what I can find. Looks like may be able to fit a vacuum diaphragm to a TB and use.....maybe.....anyway thanks, oh I will b able to get vacuum when supercharger is bypassed right? Want to make sure I have brakes!! :-0!!