Could I run safely? (OD Pulley) + How much HP gain?

The_Ghost

Registered User
Hi guys, I am looking at a couple different power-adder options to increase my boost.

To begin with, yes, I know how to use the search button and have already gone through a number of threads. It appears that 5% can be run on a stock car but it is risky. Since one of the largest sources of exhaust restriction (besides the 90* bend cats) is the resonator, which has been replaced with a magnaflow resonator unit. The cats themselves are going to be replaced with an easier bend of straight pipe. I am not sure how much backpressure this alleviates, which is why I am asking.

To start with here is the car's current setup.

Strong running 1990 5-Speed SC, makes about 6 psi at 2000 or so, and hits the proper 12psi or so it's supposed to have under load at 4700-5500ish.
All vac lines under the hood have been sealed more firmly using heavy duty zip ties as clamps. Car runs cool, and idles around 650-700.

Currently the exhaust system is STOCK except for a magnaflow resonator. I am, however, going to eliminate the cats before adding the pulley.

I am looking at a combination of the following:

10% O/D Crank Pulley
5% O/D Crank Pulley

1/2" Top
3/4" Top

What is the highest O/D I can run to the SC without seriously endangering the headgaskets with just deleted cats and a resonator?

I would like the car to look as stock underhood as possible. I am also not really concerned with 1/4 mi times so much as I am concerned with overall RWHP and minimize boost loss across the board.

I do not have a fortune to spend on upgrades, but figure that this should yield the best results for the money it costs, or more simply, best bang-for-the-buck.


Secondly, with the resonator, a 10% OD and 3/4" top on an otherwise stock 5spd SC, what kind of RWHP/RWTQ will I be looking at?

Thanks much,
Ghost
 
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Boost should peak around 2500, or around thier. If money's tight, putting a pulley on a 90 with a nearly stock exhaust is a bad bad idea. Do a good search of the forums, it will help you out alot.

If anything I would just delete your resonator or give it a tune up.

Just a thought
 
Pulley + no major exhaust work = blown headgasket

I want to go with a smaller pulley but i'm doing LT's and taking off the cats first.
 
It looks like your in California, and if you remove your cats, you will fail your emissions tests when it comes due, and then you'll be scrambling around trying to get cats to install.

I think even if you do get rid of them, you might be running on the edge with just a 5% OD if your still on the original HG's. A 15% OD will for sure kill them, AND at those boost levels you will need to upgrade your IC to at least a double to deal with the huge amounts of heat the M90 will produce. Keep in mind that the M90 not only "pumps" air but it also pumps heat the faster it spins.

A 5% is a pretty good mod for a almost stock machine if the exhaust has been opened up. Go any higher and to maximize the gains, you would then need to look at a larger MAF and T/B, which should then get you a chip so things run good.

As far as the larger top goes, its always been a discussion of interest if its a power adder or not. Most seems to think its not worth it unless your running an MPIII blower or something similar. I think its not so much a power adder, but will help keep air charge temperatures down a bit due to less compression coming through the throat. Instead of a top, I'd look into a C&L MAF first with the sample tube for 30# injectors so that 5% OD can breath a little easier.

But, its your choice and you can take the chance ;).

Frit
 
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Remove the air silencer...that's good for 3 HP.

Put a 5% jackshaft pulley on with some fresh belts and leave the supercharger pulley as is. You should gain about 15 HP and enough extra torque that the tires will spin noticably easier/further and it won't be enough extra boost to cause any problems with emissions or head gaskets.

Changing the jackshaft pulley is also much easier than changing the supercharger pulley (4 bolts) and is less likely to slip because your not reducing surface area for the supercharger belt.

A set of underdrive pulleys are also a good mod that will add at least another 10 HP.

David
 
The main reason I want a larger pulley is to make more boost at 2500.

So far as the emissions go, I fail them even with the cats on (not sure why) even though the car runs great (NoX emissions). It is NOT on the original headgaskets, they have been done at some point, though I am not sure when, I figure it was recently since there is fairly fresh RTV around the top's seal, and the PCV line is running OVER the supercharger instead of under it like it is supposed to.

Fast Freddie, you'd seriously run cats only w/ no exhaust otherwise?
What if I made a set of sidepipes running from where the cats are supposed to hit the resonator?

By the way, where in the devil is the air silencer?
 
the air silencer is inside the passenger front fender, in front of the tire. Just follow your intake tube down towards the front of the car. It will be directly under the spot where the air comes into your air filter box.
 
Okay, I dont think it's doing anything right now, but anyways I'll gut the thing.

My SC, though it generates full boost, it doesn't hardly make any noticable whine under full throttle, or at least not that I can hear. Keep in mind that I typically have my windows down since I have no AC, and I am not blasting music because there is no radio in the car.

How do I get more noticable "sc whine" or basically make the SC itself louder?
 
a K&N cone filter will make you be able to hear it much better a nd pick up some nice power dont screw with the drop in its a waste of time... metal intake tube i hear makes em louder too..
 
The_Ghost said:
Okay, I dont think it's doing anything right now, but anyways I'll gut the thing.

My SC, though it generates full boost, it doesn't hardly make any noticable whine under full throttle, or at least not that I can hear. Keep in mind that I typically have my windows down since I have no AC, and I am not blasting music because there is no radio in the car.

How do I get more noticable "sc whine" or basically make the SC itself louder?

Don't gut it, you remove it entirely. Once removed it will have more whine.

David
 
yeah i got significantly more sound

when i took the air box out, the silencer, and added a metal tube from the maf into the fender with a cone filter.

no overdrives here
exaust is 2 HF cats, and no res, y pipe into two mufflers.

making great boost with that setup. around 10-11. spins the tires with ease.

i only have the 6 inch cone filter. i think the stock maf flows like 550cfm, so i didnt need a fattty 11 inch filter that flows 2200 cfm.

waste.
 
Some Things To Think About.

It's really all about how much money you want to spend and make sure you do it in the correct order. If you don't have enough money to do it right the first time then leave it alone and just wash and wax the car until you can put together a wish list fund.

Over three years ago I picked up a 90 automatic (wish I had a 5speed) with 64000 miles for $3500.00. The first thing I did to it was replace the exhaust from the heads all the way to the tail pipes. Don't be in a big hurry to get that 10% pulley installed on the blower until you have done the exhaust first and correctly.

This is what I did. Other people will tell you differently.
  • I purchased a set of exhaust manifolds and sent them to tbird88 for porting and coating.
  • I won an ebay auction for SCP down tubs/high flow cats/Magnaflow res already welded together.
  • I bought a used Flowmaster Force II exhaust from a guy that parted out his 35th.
The parts cost was about 1/4 of what you're going to pay for headers and brand new exhaust parts.

I took it to a local shop and had them assemble/install it. They had to make a fitting for the resonator to the exhaust pipe because one end had a yoke and the other end was for a fitted exhaust, so that cost extra money. The job of replacing the exhaust manafolds wasn't cheap because several parts had to come off to do it.

Here's the up side. The first thing I noticed was the sound of the exhaust was nice and throaty. The response appeared to be better at lower RPM's and there was considerable reduction of back pressure.

Here's the down side. I lost about 3PSI of boost and some power at the mid rpm range but I got it all back plus when I added a 10% blower pulley. Once I added the blower pulley my car stopped running right about 50 miles later and I had to tear down the entire intake system and reseal all fuel and vacuum lines to get it back. What a mess that was but I was able to do that all myself.

I don't have all the receipt anymore but the exhaust job and blower pulley parts cost me in the area of $450.00 and another $400.00 is labor and that was 3 years ago.

Now take into consideration that since I've done that one upgrade I've had the car in and out of the shop every year for some major problem.
  • Gas Tank Seal, Fuel Pump and Pig Tail
  • Left and right Upper and Lower Control Arms
  • Left and right Tie Rod Ends
  • Rebuilt AOD with shift kit
  • Solid Front Motor Mounts
So since I've purchased this car, I've sunk about $5300.00 into it and if I were to sell it right now I bet I couldn't get more then $2500.00 for it.
 
I just want to beat my buddy's stock 03' WRX.
Bastard needs to be taken down a few notches.

I have a 5-speed, therefore, I should have a good 10-20hp more going to the wheels than an automatic, right?
 
The_Ghost said:
I just want to beat my buddy's stock 03' WRX.
Bastard needs to be taken down a few notches.

I have a 5-speed, therefore, I should have a good 10-20hp more going to the wheels than an automatic, right?
From what I've read, the 5speed is faster but all the HP isn't gonna do you any good if you go up in a puff of smoke.
 
The_Ghost said:
Strong running 1990 5-Speed SC, makes about 6 psi at 2000 or so, Ghost


Man, I am at zero at 2800 RPM according to the Aux Box. But then again, my car is far from stock. As far as your question, I wouldn't overdrive your SC anymore than 5% with your setup, and preferrably via the JS. 3/4" top too. 1" would seem like overkill, unless you had additional mod plans for it down the road.
 
pablon2 said:
Man, I am at zero at 2800 RPM according to the Aux Box. But then again, my car is far from stock. As far as your question, I wouldn't overdrive your SC anymore than 5% with your setup, and preferrably via the JS. 3/4" top too. 1" would seem like overkill, unless you had additional mod plans for it down the road.

I said 1/2", not 1".

Reason being for fitment with the stock i.c. piping.
Why overdrive via the jackshaft and not the crank or sc pulley? I figure the SC pulley is harder to change and slips easier but why not the crank pulley?

to the poster above pablon:

I am being very careful in planning so that the engine will not grenade and I will not have to hassle with headgaskets. Those are a bitch and I do not have the time to do headgaskets; the SC is my daily driver and I work full-time.
If I drove my E-150 to work more than like once I would be putting my entire paycheck into going to and from work thanks to its abysmal gas mileage.
I would like the SC to beat the WRX if at all possible, but I am not going to do anything if it is more than a 40% chance of serious engine damage.

By the way, the car is safe to rev to 5500, correct? I always shift at 5 because the red checks at the end of the tach look almost like the "DONT FREAKIN REV THIS HIGH" lines. It should be safe to 5500 since the 3.8 in our 00' mustang revs there without a problem.

-Ghost
 
The_Ghost said:
I said 1/2", not 1".

Okay, my bad. So your choices are 1/2" and 3/4". Do they even make 1/2"? Personally I would go with 3/4" (and I do :) )

The_Ghost said:
Reason being for fitment with the stock i.c. piping.
This shouldn't be a prohibitive reason b/c all IC joints should be loose when assembling the IC ductwork. Helps to remove the support bolts too. Two schools of thought exist on doing that. Some say don't and people like me say do, b/c if you don't then you are going to have a hard time lining everything up and may have a boost leak due to poor joint seating/fitment.

The_Ghost said:
Why overdrive via the jackshaft and not the crank or sc pulley? I figure the SC pulley is harder to change and slips easier but why not the crank pulley?

I believe ODing via the JS pulley is the best of both worlds. Here's why I think this: belt slippage can be an issue if ODing from the SC pulley. The crank pulley is the best place to OD, but it is harder to get on and off than the JS pulley. Plus, who wants to mess around with something that screws into the balancer and risk messing up the threads due to the ~1/4" hole offset on the balancer if you aren't paying attention when bolting it on. SO, the JS is the best of both worlds.......easier and "safer" to swap out and also reduces chances of SC belt slippage. (just make sure to leave the JS-SC belt on when initially loosening the 4 JS bolts otherwise you'll be scuffing knuckles.) :D

The_Ghost said:
to the poster above pablon:

By the way, the car is safe to rev to 5500, correct? I always shift at 5 because the red checks at the end of the tach look almost like the "DONT FREAKIN REV THIS HIGH" lines. It should be safe to 5500 since the 3.8 in our 00' mustang revs there without a problem.-Ghost

On a fairly stock SC with miles, I personally would not shift above 5,000. Our engines run much hotter than the stang 3.8s so I'm not sure that is a wise comparison. More RPMs = more heat, especially in our SC world.
 
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