10% and no more boost than stock????

turboken

Registered User
Howdy everyone. I have a 10% pully with exhaust mods, and a shorter supercharger belt. I am still only getting barely 11 PSI. No check engine light, no gas smell, no noticable problems. My tranny has no OD and is in the process of killing itself, could this cause a problem somehow (i dont know how)? I was sure that the smaller belt XXXX390 would fix it. Help?
 
Have you checked to make sure you dont have any boost leaks ? Also i would put an aftermarket boost gauge on it and see what it registers.

I had a 94SC with a 8% that had a bad boost leak right near the connection for the boost gauge. I fixed the leak and the thing started to take off like a bat outta hades.
 
how old is your belt?or maybe your tensioner is shot= belt slippage...you have a 88 supercharged turbo coupe?
 
No, I have both a TC and SC. I haven't checked for boost leaks. I assumed that if there was one, it would trigger the check engine light. I can buy some propane and check it tomorrow. Where does the boost guage attach on the 93 auto car? thanks guys.
 
Did you do the 10% pulley and the exhaust mods at the same time? If so that could explain why you didnt get more boost, sort of. More freefroling exhaust will reduce boost.
 
well, i had the blower rebuilt and a 10% put on. I was scared of blowing HG's, but since i cant drive till august (seizure), I did it, then got the exhaust done later. before the exhaust, i got on it without flooring it, and the boost went between 10 and 15. Once the exhaust was done, I would say it gets 12 right at 5000 RPM. I dont get a check engine light, and I cant tell any boost leaks. I used Mapp Gas (out of propane) to check for leaks on the parts I took off. no change. It feels slower than it was. I measured the pullys circumfrence with teflon tape (I know, it stretches.. I was careful). the stock one came to 3.0245 diameter(close) and the 10% came to 2.8653. so it is a 10 %. I dont know what to do. My auto tranny is FRIED. no OD and when locked into 2nd, it slips below the rpm it wants to be at, but give it gas and it pulls hard from where it wants to be at. (example.... 2nd gear wants to cruise at 3000 RPM. locked into 2nd, it will drop rmp like neutral until you give it gas and it jumps to 3000, and pulls hard from there). could this or a torque converter cause problems?
 
I have true dual exhaust andquite a bit of porting done, with a 5% pulley I get 11.5 lbs of boost. If yours went down. From 12 to 11 then maybe the belt is slipping.
 
with a new tranny (ford) and this cold weather, I can now hit 15 psi if I go 6000 or above. I don't like that tho. when it shifts itself, i see about 13 psi.
 
My '95 SC 5spd only hits 12-13 psi with a '91 SC pulley, 5% overdrive jackshaft pulley and manifold back exhaust with no cats. It's basically right back where I started when it was stock. I've checked for boost leaks and never have found any but I'm going to check where it hooks up to the gauge now.
 
The most important thing is increasing the volume of air moving through your engine. The PSI reading on your boost gauge is only showing how much restriction to air flow through your engine there is.
Lower boost readings after modifying the exhaust means there is less restriction and thus more air moving through the engine.(a good thing)
High boost readings on an SC is not a good thing.
Remove restrictions until your boost gauge reads 8 PSI and you'll be moving more air through your engine than a guy running 16 PSI.
 
So me running 14-15lbs of boost isn't good? :D

The back half of my exhaust is changed, but not the front half (doing in the spring) Also have a 94/95 blower with 5% OD pulley.

-Andy "Melon"
 
Melon said:
So me running 14-15lbs of boost isn't good? :D

The back half of my exhaust is changed, but not the front half (doing in the spring) Also have a 94/95 blower with 5% OD pulley.

-Andy "Melon"

No, you're still pretty restricted. Redo the rest of your exhaust and watch the boost drop, but you'll be moving more air through the engine. :)
 
Well you want some boost. It is true that as you free up restrictions in the exhaust the boost will drop. I went to a 5% overdrive pulley on my blower and a 5% javkshaft pulley. My exhaust is true duals with only mufflers and thats all. I get 13.5 pounds of boost now. The important part is that the boost comes up right now and there is almost no exhaust restriction. Do the front part of your exhaust and you will see a gain in power. I took off the low restrriction cats and now the car is really loud. :eek:
 
Thats true Tim you do want some boost pressure. The Eaton M90 is setup to be most efficent at 8 PSI anything higher is actually a reading of backpressure ie restrictions, not to mention extra unneeded heating of the charge air.
 
turboken said:
No, I have both a TC and SC. I haven't checked for boost leaks. I assumed that if there was one, it would trigger the check engine light. I can buy some propane and check it tomorrow. Where does the boost guage attach on the 93 auto car? thanks guys.

I to had the same problem and checked it over and over again with propane and no leaks. I made an adapter to hook into the intake tube running in to the TB so I could actually pressure up the system. At 6 lbs of pressure I had leaks at every connection, at 9 lbs air was blowing every where. I tightened up every connection untill it will hold 14 lbs with no leaks. I even had the ford dealer do the propane test and they found nothing wrong. I am not a fan of that test. At idle you have a vacuum at the connections so it will not tell you when you have 10 lbs of pressure and a leak. My car even had a bad idle that would never go away as many of my good SC friends can tell you. It idles perfectly now. My 2 cents anyway
 
It seems to be a trade off between making boost and intake charge temp. At 13.5 lbs. I feel like I am pushing it. I cant figure out how some guys can run 18-20 lbs. of boost. that has to create a lot of heat. And it takes a lot of power to turn the blower that fast.
 
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