88 comanche and a M90 blower awd build.

They didn't use a BOV. It is just a 1 inch bung for that hose that routes from the charge pipe to the bypass valve inlet. Kind of like how the stock Thunderbird setup was just way shorter.

Here is what I think. As long as the vacuum line for the bypass valve actuator is routed to AFTER the throttle body(Intake manifold), It will see vacuum as soon as the throttle closes and open the bypass butterfly fairly quickly even if there is still boost in the charge pipe. The question is how fast does does the intake manifold go from boost to vacuum after the throttle is closed. If it is almost instant then it might be safe. If it is a few seconds then that may be not a good idea and too much pressure will be on the throttle plate.

A BOV would be the best way to do it for sure.
 
Solarbell, I also meant to ask you: How does the PCV system need to be routed. Does it need to be rethought for boost? I know the answer might be in your thread but i'm still on page 4...
 
I never really talked about it. So long as one line goes to the somewhere that sees continuous vacuum it should be fine. The other end I just stuck a tiny accessory air filter on for the incoming air. (you can see it in some of the pictures)

Thing is, vacuum is generated by the butterfly valve of the throttle body and the pull of the engine. If you run in a blow-through setup I don't think you will ever have continuous vacuum anywhere. You may run into issues for all the items that require vacuum such as the A/C system, etc.
 
embs2001 said:
Here is what I think. As long as the vacuum line for the bypass valve actuator is routed to AFTER the throttle body(Intake manifold), It will see vacuum as soon as the throttle closes and open the bypass butterfly fairly quickly even if there is still boost in the charge pipe. The question is how fast does does the intake manifold go from boost to vacuum after the throttle is closed. If it is almost instant then it might be safe. If it is a few seconds then that may be not a good idea and too much pressure will be on the throttle plate.
Click to expand...

That valve is not instant. Nor is the transition instant. Not 10 seconds, but not instant either. The propagation time down the hose is surprisingly long. I moved my connection for the actuator from the factory intake manifold to a new fitting right on the discharge hat to take 2' out of the line just for that reason.
 
Thats how I have mine set up now, vacuum on the rear and little filter on the front. Where is your catch can in the system?

Well I guess we will figure it out when I try. I still think the intake manifold will still see vacuum unless the throttle is opened enough.
 
The more I think about it, the more I see a BOV being necessary with blow through. I really do not want to blow up my throttle body and send shrapnel into my motor.
 
embs2001 said:
Thats how I have mine set up now, vacuum on the rear and little filter on the front. Where is your catch can in the system?
Click to expand...

Here.



Well I guess we will figure it out when I try. I still think the intake manifold will still see vacuum unless the throttle is opened enough.
Click to expand...

Any time you are under boost the original intake manifold will not have vacuum. The question you have to answer is whether or not that will be enough. This is a Renix motor which I know little about. Does the distributor have vacuum advance?
 
Yea i knew it would be under pressure when in boost, i was just saying as soon as you are done boosting and you snap the throttle closed, everything after the throttle should snap right back to vacuum.

I dont see any vacuum advance, I think that was before renix maybe 4.2 IDK.

I have vacuum for FPR, MAP, Brakeboost, CCV, Vent control, horn?, All of witch will be fine during short term boost. I will just zip tie all the fittings so they dont pop off.
 
I can't tell from your picture. On the catch can you have the inlet from the rear CCV on valve cover, and the out let to intake port?
 
embs2001 said:
Yea i knew it would be under pressure when in boost, i was just saying as soon as you are done boosting and you snap the throttle closed, everything after the throttle should snap right back to vacuum.

I have vacuum for FPR, MAP, Brakeboost, CCV, Vent control, horn?, All of witch will be fine during short term boost. I will just zip tie all the fittings so they dont pop off.
Click to expand...

Personally I think it's a bad idea. But hey, I've only built one setup and have never tried it that way so I'm open to be proven wrong.


embs2001 said:
I can't tell from your picture. On the catch can you have the inlet from the rear CCV on valve cover, and the out let to intake port?
Click to expand...

It's actually an air/oil separator, not a simple fluid catch can, because the oil is entrained in the air and an open space won't catch the oil. From rear port on valve cover to input of AOS, then from output of AOS to vacuum source. Front port of valve cover has the small air filter.
 
I noticed the stock injectors were leaking so i decided now was a good time to install my larger ones. They say 32lb but that is at LS1 pressure.

20150217_221718_zpsoj6tryru.jpg

20150217_221648_zpsyuhs5xw7.jpg

20150217_221754_zps6wzwy52t.jpg

20150217_193117_zpshlkrhtyg.jpg
 
embs2001 said:
I have vacuum for FPR, MAP, Brakeboost, CCV, Vent control, horn?, All of witch will be fine during short term boost. I will just zip tie all the fittings so they dont pop off.
Click to expand...

You are going to want to use one way valves on most of the vacuum for accessories and emissions stuff if they don't already have it. The brake booster already has one on it.. no need for that. FPR(rising rate?) and MAP of course will need to see boost. The CCV needs some solution. You don't want to pressurize the crank case. Perhaps a PCV valve might work for that.
 
Thanks, Ill get some check valves and look in to the PCV.

Well a friend of mine actually is letting me try out his votech FMU. Right now I have the stock 1 bar map and I was wondering would it be better to put a check valve on it or let it see boost. I had my volt meter backprobed to the MAP and I noticed when I blew positive pressure it would go well above 5v. What does the computer do when it sees over 5v? I know the stroker guys use adjustable maps set higher than 5v for a richer mixture however I also read boost makes the map throw funny voltages. I was thinking of put a check valve in so it will see 5v at 0 boost and let the FMU take over from there. I also thought about using a GM 2 bar map with a MAP adjuster to give me a tuning point.

I know you guys might not agree with using a FMU for now its all I can do.

I appreciate you guy's help!
 
Today I installed colder range plugs with .030 gap. Next time im at the pump Ill fill up with 93 octane. I replaced the oil in the blower with GM SC oil. I still need to order AEM wideband, boost gauge, fuel pressure gauge. silicone hose, and clamps.

Ill try and test fit the blower and snap some pictures here in a few days when it warms up.
 
Installed the blower today. it just barley hits the hood but I should be able to get it to close. Im going to need a little longer belt and a different upper radiator hose. Here are some pictures.

20150223_180650_zpsijlc2rlf.jpg

20150223_171816_zpszsch58ml.jpg

It hits somewhere in this area. Notice how there was almost a perfect impression for the blower hat.
20150223_171810_zps5houlvxj.jpg

20150223_171455_zpscinxgro5.jpg

20150223_171519_zpsk0v1slix.jpg

20150223_171421_zps41m0rdok.jpg.html
hood closed
 
Last edited:
You must log in or register to reply here.
Back
Top