91 SSE, exh/intake/ignition for best MPG - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-28-2007, 07:03 PM   #1
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Default 91 SSE, exh/intake/ignition for best MPG

Just curious if anyone has messed with exhaust, intake, or ignition on the 87-91 3.8 and what kind of effect it had on fuel mileage.

My cat is plugging up, im going to cut it out, and I figured I could weld up a whole exhaust for the beast while im down there, I have plenty of spare pipe laying around.

I was thinking for exhaust, I would do a true dual, no cats, with an h pipe or similar, diameter of the pipe being exactly what the collector on the header measures(not sure what it is until I pull em). Will this provide enough backpressure for my 3.8? I plan to run more restrictive style mufflers, no flowmaster or straight through rice garbage. This is my daily driver, im not trying to make my slow bonneville attract attention. My other car sets off alarms, I try to keep low key in the bonne.

on the intake, my plan is to run a k&n filter, and replace the factory accordian with a straight 3 in. pipe. also I am going to get a JY lid to experiment with ducting hoses into the front bumper/airdam. I do not want to run an open element air filter, I dont need the noise, and I don't need to worry about my motor inhaling water.

My coils are not so healthy anymore also, anyone know of any aftermarket coils for my car? I'd like to run msd, or accel, anyone running anything like that? if so did you notice any increase in mpg?

My goal here is to increase throttle response, and get better gas mileage. All of which will be done by cutting the cat, replacing with a striaght pipe and replacing the coils, I know this. But hey, I can't help wonder how much of a difference the other stuff might make, im a gearhead, and especially since everything but the mufflers and k&n is free, just a little work.

I appreciate any info, thanks
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Old 09-28-2007, 07:54 PM   #2
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Go with a high flow cat... Keep the back pressure... The 3800'* do really good with some back pressure.. Kill off the back pressure and kiss a chunk of torque goodbye...

For the 91 you can adapt to the Type II Delco ignition set up with the 97+ SSEi Blue coils( These coils will have a blue strip on the bottom ), the Bluies will fire a bit hotter.. This should give you better throttle response..

You can go with the true dual, but even a single side double outlet would serve the same purpose.. Same goes for the camaro firebird muffler... I think a couple people here and on the Lesabre forum have done a true dual exhaust... Looked very nice too.. Any of them would work..

Getting the intake to flow a bit more will help the 3800 LN3 as well... These things make good strong torque, and it gets better with a little more flow into the motor..

also do you have the 2.97 or 3.33 gear ratio?

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Old 09-29-2007, 02:55 AM   #3
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Not sure on the gear ratio, I do have all the origianl paperwork for the car though. Is there a quicker way to check maybe by the vin code or plate on the vehicle?

all the high flow cats I have seen have been straight through, and some were straight through but had a bit smaller diameter inside. I think I am going to build the exhaust, and if I do notice low end loss, I can always cut it apart and weld a restrictor into the exhaust, or put a cat in down the road. My goal on the exhaust here is cheap, and reliable. I dont want any burnt exhaust valvles how finicky are these 3.8'*? I do not want to spend a whole lot on somthing that really isn't going to make the car a whole lot faster. I will spend money on ignition and intake because I feel it is more important for making the engine more efficient, plus my coils are going bad anyways. This is my daily driver, I already have a project car/money pit, I just want my dd to run as reliably and efficient as I can within my means.

For now, I am just going to cut out the cat and weld in a straight pipe, leaving all of the rest of the existing exhaust. the stock muffler and piping should provide enough backpressure shouldn't it? I want to go true dual soon because I think it will sound better than a single in dual out, the pipe is free, and I just like building custom parts for my cars.

I want to get the ignition and intake sorted out before the exhaust. What else needs to be done to upgrade to the blue 97+ssei coils? Is it just a plug and play upgrade or is there rewireing of the connector or anything like that?? maybe a custom mount?


thanks for the info
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Old 09-29-2007, 11:15 AM   #4
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First of all, we have NFC what engine you have. Please put your year and trim level in your signature.

Don't open your exhaust and then put a restriction in. That'* gauranteed to hurt performance.

Do NOT straight pipe the CAT! You WILL lose low end torque, and it doesn't matter which engine from 87-2005 you have. Besides, I could use the EPA $250 reward for turning you in. If you live in the States, running a cat is a FEDERAL LAW. Enough reasons for you?

Everyone here that straight piped on a stock or nearly-stock car HATED it. I ran for a short time cat-less (due to budget) on one of my L67'* and saw exactly the same thing. Bottom end came right back to me when the cat went in.

Not sure how you're going to go true dual exhaust on a car with a transverse mounted engine, but you won't gain from it. Look at our top 25 list. None are true dual. And only a couple are running catless. They flow alot more than you probably do, and they live in Canada where it'* not required.
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Old 09-29-2007, 05:19 PM   #5
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Willren, I simply asked what others have done and what their experience was pertaining to fuel mileage. I am well aware what the effects of unrestricting a N/A exhaust will do. low end is lost high end flow is gained, this is an obvious. I wasn't aware how dramatic the effect is on these cars because I am not a bonneville guru, this is why I ask questions on this forum.

IN THEORY, a restriction is a restriction, no matter what causes it, period. be it a cat, a smaller diameter restrictor, or a potato, its all serving the same purpose, RESTRICTING THE EXHAUST, yes i understand the cat serves another purpose also, just trying to prove a point.

now I haven't cut my cat or anything so don't call the EPA on me buddy, but True dual on this car would not be hard, I just looked underneath the car and there is even enough room for two cats. Theres plenty of room to route exhaust. and yes I agree that it would not gain any performance over a well flowing single exhaust, but if the backpressure is up to par with what the motor needs it will not hurt either. I gaurantee you it would sound better, which is what I'm going for. I do not like the sound of single exhaust on a v6, i've heard single vs. true dual on many v6'* always preferring sound of true dual.

Im not trying to mod this car for performance, it is slow and handles like a wet mitten, not even a performance car platform, its heavy and FWD. This is my DAILY DRIVER, I want to get good gas mileage I have floored it twice, once when I got it and once the other day after I fixed a few problems. I didn't buy this car because I thought I could ever make it fast, even if it had 400 hp and ran fast quarters it still can not go around a corner worth a hoot. Don't get me wrong I like the car, it has comfy seats and I dont mind driving it every day, thats why I want to make it run as efficient as possible, while keeping the motor itself 100 percent stock.

Anyone got any info about the ignition mod? I found accel coils for the car that put out 45,000 volts and are a bolt in replacement. Anyone know what the stockers put out or even the 97+SSEi blue coils?

thanks for the info guys
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Old 09-29-2007, 06:00 PM   #6
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I can't say for sure, but I have heard that the Delco Type II coils are in the 60,000 range... I have this system on both the 91 SSE( Toy car, Fixer upper ).... and the 91 LE as well... Both responded nicely... Not what I'd call an HP improvement, But both seem to have better starts, slightly smoother idle, and a little more throttle response..

To get the most Mileage out of the car I would recommend the Delco Type II system, Possibly some NGK TR55 plugs, or the TR55 Plats.. among a few other plugs... also replace the O2 with an AC Delco or Denso unit.. Possibly a K&N drop in filter.. All of these should help a bit in the mileage department..

as for the Transaxle ratio... Look on the spare tire cover for the RPO list... You should have

F79 for 2.97 or

GX3 for the 3.33 ratio..

With the 2.97 ratio 30-32 on the highway should come pretty easy.. with the 3.33 ratio 27-29 would be the general highway numbers..

If you look, I would also like to know if you have the 1SA or 1SB code..

with the 1SB code you usually have Leather and a sunroof.. Thats about the only difference between the two...lol

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Old 09-29-2007, 07:50 PM   #7
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I looked, and I found out its a GX3, and also 1SB codes.

It has leather, sunroof, everything basically. Im pretty sure it has all options but a cd player.

Do the delco type 2'* just plug into my 91?

thanks
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Old 09-29-2007, 08:20 PM   #8
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Yes, they bolt up and plug right in. The LN3 runs much more efficiently with them.
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Old 09-29-2007, 08:44 PM   #9
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cool looks like im going to pick some up this week, local parts store has them in stock 20 bucks per coil.

But this gets me thinking, technically I could use whatever MSD has as an upgrade for the 97 model right?
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Old 09-29-2007, 08:55 PM   #10
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Woah, woah. You need the ICM too. 3 coils and an ICM is going to cost one heck of alot more than $60 if you buy it from a parts store. Just go to a junk yard and grab em.

Also, no, it is not worth it to upgrade any further. Those coils are plenty hot.
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