Any intake or exhaust mods to increase power?

[Guest imported_lbowejr]

I purchased my 90 coupe in Jan 2004. Are there any minor intake or exhaust changes that will boost power? How about a chip? I don't want to get into anything to extensive. Also, what about factory carpet replacement? Thanks.

[RangerRick]

I've dabbled here in a few. Exhaust mods are quite extensive...tips are about the only thing you could do, and those are even hard as the dual exhaust is clipped together. Some things I've done, or am considering doing:

1) Exhaust - replace the exhaust with something not to add noise but strictly to add a tad bit of power. Keep in mind these engines are not designed to be street racers, and are not at the top of any racing lists. Get this professionally done unless you have extensive exhaust expierence.

2) Intake - this can be done on your own. For starters, clean your existing air box/replace the filter. The previous owner of mine had not done so for years and it appeared as if it was a forrest. Once cleaned, a noticeable improvement occured. You can remove the stock air box and replace it with a cold air intake, provided you build your own stem off the throttle body. It is roughly 3.5 inches, if I recall correctly, and then can be routed either down under the body (keeping in mind your minimal ground clearance) for a forced air intake, or simply in the engine compartment for a better cold air intake. I chose to stem off the existing air box and add a forced air intake with breather valves.

Just some thoughts, they do wonders for a car!

[RatReatta]

while this may sound funny, i noticed a big improvement by removing the stock airbox completly and slapping on a 15$ coneairfilter for like a civic. i recently began a project to make cold air or ram air by running piping from the air hose to a k&N that sits right behind the grille and mounts down to the top of where the gaurd does. i have the next three days off so i think im gonna finish it, it works but looks hedious right now, and ill post pictures and maybe a short how to

[Guest imported_lbowejr]

Can you tell me more about the forced air intake with Breather valves? I dont know exactly what that is. Is there a kit or did you fab? What kind of performance improvement did you get? On the exhaust, I replaced the catalytic converter and muffler with low back pressure products but I did not notice any difference. Thanks.

[Guest imported_lbowejr]

Anyone else have any advice on improving performance without a major overhaul or supercharger? I'm not looking for miracles.

[padgett]

Perhaps this should be in the FAQ, it comes up so many times. Just about everything in the "C" engine is at its limit, anything meaningful is going to require at least an "L" engine which is just enough different that major parts will not swap.

The "L" engine, even though only rated at 5 hp more has a better intake (can flow about 30% more air and has 22 lb-hr injectors instead of 19), heads, and exhaust. It is also the basis for the supercharged version.

The good news is that "L" engines are plentiful in junk yards and many were found in Park Avenues, LeSabres, and such that probably led relatively pampered lives.

If you go this route, be sure to get all of the accessories (MAF, ignition assembly, injectors, etc.) that go with the "L". Wouldn't hurt to get the later "E" transmission at the same time but now you will need PROM and ECM changes to run it.

However now opening up the intake air path and exhaust system will make a difference. If you want to look stock I believe the air cleaner assembly used on late 3.4 Aleros and such with the A1279C filter might fit, otherwise a cone air filter with a cold air box and 2" snorkle would work.

As to a cam, I would probably want something with about 205-210 degrees duration at .050". I prefer a touch more exhaust than intake but that is me. There is not a lot of choice for series I 3800s.

[Guest wally888]

Re. the picture of restricted exhaust you recently posted, same in all years?

[Guest Greg Ross]

That problem manifold is on '88 thru '90 3.8 L engines. The improvement came in '91 with the introduction of the Series I 3800 using a totally different style rear exhaust manifold. As well in '91 a 2-1/2" dia. exhaust system was used on Reatta to improve breathing..

[padgett]

I cannot help wondering if the 88-90 ("C") 165hp rating and the 91 170 hp is more marketting than reality. For instance the 88 used a slightly more aggressive cam than the 89-90 but there was no change in specs. OTOH there were significant increases in both the intake and the exhaust systems for 91 ("L") - 30% increase in throttle body flow and increase from 19 lb-hr to 22 lb-hr nozzles give a measly 5 hp increase ? I doubt it though they did keep the same somewhat restrictive air cleaner and air horn.

GM has always played games with HP but usually the torque curves are pretty accurate

[Guest imported_lbowejr]

What about just rebuilding the C series with bigger pistons, more agressive cam, and oversizing the valves? Would this be as good as the L series (or is it the I series)?

[Guest Greg Ross]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Are there any minor intake or exhaust changes that will boost power? How about a chip? I don't want to get into anything to extensive. </div></div>

A rebuild of that extent would be a long way from where you started this thread.

As padgett said initially, opening up intake and exhaust and then recamming to generate flow is the most you can accomplish normally aspirated. When I started my project 2 years ago I took a Goodwrench reman. 3800 Series I, got a lumpier Cam from Crane Cams, changed the exhaust system to the 91 2.5 inch dia. (a 30 % increase) and used a larger snorkel on the front of the air box.

Had a response back from the fellow who is now running a 3800 Series II in an eBody, he does his own programming but for this is still using the original ECM but programmed in his case for the supercharger. Also did away with the EGR.

Unfortunately there is no magic bullet, chip or 5 minute fix. Horsepower takes work and changing one isolated factor cannot have much benifit.

[padgett]

Biggest problem with just rebuilding a "C" with "bigger" (suspect you could get to 4.2 liters with stock components) is that the intake system is so limited. The "L" snakes system can flow 30% more air and the injectors are 16% larger (normally aspirated). Right there is your limiting factor and you apparently cannot put an "L" intake on "C" heads (possibly with some modification, haven't looked into that).

[2seater]

You can crank up the power a bit by simply installing the vin L pistons in the vin C engine. The "L" pistons have a higher compression height and bolt right in. As far as I know, the first 3800's from '88 on are the Series I, the series II appeared somewhere around '95-97. Boring the engine larger will increase the compression ratio all by itself, if all other things are equal. The overbore limit seems to be .040". I do not know if the later model vin L manifold or throttle body will fit, but, the stock throttle body can be bored about 5mm larger and a new throttle blade installed. The rear manifold is restricted, and it can be corrected, but it may be possible the vin L manifolds will bolt right up, which would be an improvement. Using otherwise stock components, if the intake air box is replaced with a cold air intake and some mild massaging is done to the heads, it should yield 192-195 hp. A little hotter cam would help even more. A Padgett pointed out, the '88 cam has more lift but less duration than the '90 cam, but yet hp ratings are the same? I do not know if the vin L cam has any performance advantage, but I do know the fastening system is a little different, so all drive components for the cam would need to be vin L. The stock 18.8 lb injectors can easily support 200 hp, even more if you want to push the pressure higher.

[Guest imported_lbowejr]

You mentioned that the rear manifold is restricted and that it can be corrected. How do you correct it? Thanks.

[bigsteviejoe]

I haven't looked at the RC-calculator lately, but based on the power output vs injector sizes, even though the computer goes up to 170gm/minute, the supercharged 255, it seems that the Reatta computer was programmed to underutilize injectors.

Probably cuz the FI was still fairly new. With hi end Reattas and they didn't want to jam or overheat the injectors.

Right now Tranny control units, or the last I saw were $700.

Reboring a the 3800 for power, will probably equal the cost of turboing or dropping in a L67 with oversized injectors. From then once you have a close size of injector, in this car 24s seem to have issues with boost, i feel its just a matter of tuning, with a universal piggyback. The rest is pump & regulator.

The N/A engine just right now doesn't get enough air, in and through it. I think of it as a sleeping giant. All it took was a little compressed air.

For intake, hard core intake, you'll probably have to go pretty radical to get some kind of result, 1 or 2 cones, in front of rad, mandrel bent pipe, then maybe angle cut the leading edge of the pipe where the cone is supposed to go is shorter, the back longer, angle it so the cone is slightly angled forward so goes in hits the pipe and goes in. Maybe tape up a portion of the backside of it so air can't escape through the back. With 2 cones just build in a Y in the piping if possible. As a agressive a CAI can get. Worst case: putting CAI in front of rad and it isn't enough, you have plumbing for an intercooler .

Those 24 valve engines, do freakish things compared to the C or even the L. GM Ross got a well designed all round cam, with in mind that he might boost sometime. Boost involves a less aggressive cam than street NA engines, so you can go more agressive. Instead of 10% more, how about 13-17% more.

And then you have the miniscule exhaust. At the very least make sure the rear manifold restriction is gone. HIGHest flowing cat., 91 or custom mandrel catback, highflow muffler.

The cooling system sucks as is. I really need to be getting rid of the front plate soon if this weather continues. Should I be worried at mid 220oF? Will water wetter help lower temp much? Programmable fan, or high fan switch would be useful.

A well placed vent that they put on hocked up ricers may help keep the engine from getting so hot.

You can lose 6-7 lbs of rotating mass per wheel, if you get good cheap lightweight rims even if you went to 16s maybe 17s. I can't see how this cannot give some sort of seat of the pants improvement, not only in acceleration, but braking. You benefit from having 12-14lbs less of rolling mass, acting as drag, end result less tire spin, cuz there's less inertia. Helps transmission too, less inertia the tranny has to go against from having to turn heavy drive wheels. Maybe I'm overstressing this but with 1/10th scale RC cars, rotating mass vs non rotating was factored like 10 times normal mass. Unsprung weight is also reduced. There's light weight lugs too but from there you only lose a pound and air tools are a no no.

I don't really have any idea of which is lighter, more rim less tire, or less rim more tire?

Only thing after that the only thing I can think of is have the intake manifold massaged.

LOT®'s

[padgett]

If off the car, you can open up the rear exhaust manifold with a die grinder. Might be able to do from under the car by dropping the head pipe but would want REALLY good face and eye protection.

NA and boosted engines really want entirely different cams and combustion chambers. For NA you optimise the intake side and use overlap to assist in scavenging and increase the charge velocity. With boost (and particularly turbosupercharging) you optimize the exhaust, reduce overlap and open the intake sooner. You also have to be careful to avoid choked flow (when an intake charge tries to go sonic - there is some Rocket Science there 8*).

Opening the chamber (spherical is best) lets a boosted engine increase the charge mass without exceeding chamber pressures suitable for pump gas.

That last is something I had trouble wrapping my mind around for a long time. For a given octane of gasoline there is a maximum chamber pressure (also depends on chamber shape and location of the spark plug(s)) that can be realized without detonation.

With a normally aspirated engine that is a function of efficiency (as an air pump) and compression ratio.

With a boosted engine you can achieve that chamber pressure value with any compression ratio and as you lower the compression you also increase the chamber size so for that specific pressure, you can put more fuel and air inside which means more power per cycle.

Now there are limiting factors but for pump gas and boost up to 12-14 psi that is the basis. The other factor is getting the charge past the valve without going sonic (see above).

This gives you a problem with valve size which is limited by the chamber geometry and particularly the cylinder bore.

In other words a good cam for N/A use is not the best choice with boost and neither is the piston shape the same.

Does that help ?

[Guest imported_lbowejr]

Yes. Thanks. If I replace the engine with an L type, what are the major components that are different? Is there any custom brackets and so forth that must be fabricated? What parts do I need to make sure I get from the salvage vehicle? Thanks.

[padgett]

Make sure you get the computer and Prom. Wouldn't hurt to have the engine and dash to computer wiring harness also.

[2seater]

Most auto makers run the injectors at a fairly low duty cycle, maybe 75%-80%, partly to keep them cool and give long life, plus an extra margin if they start to plug. For most all around driving, they rarely see even that, and you can calculate how hard yours are working by simply watching the injector pulse width. At 5000 rpm the total time available to inject a full fuel load is 24 ms. You can also play with fuel pressure to change the delivery. For example GM runs a 22lb/hr injector at the standard 3 bar or 43.5 psi in one model of 350 and Ford uses an equivalent injector at a lower pressure of about 36 psi in the 5 litre at about 19 lb/hr. Larger or smaller injectors themselves do not directly impact the power output, except when it goes to full fuel mode at high throttle opening. There just needs to be enough to avoid lean out (bad), and yet be small enough for the ECM to control effectively. I am running a 24 lb/hr injector @ 3.5 bar for about 26 lb/hr, which seems to be close to what the stock ECM can control. In some cruise modes, the BLM is down around 100, so the computer has adjusted a long way to keep the Integrator around 128.

As for wheel size, larger wheel sizes seem to slow the acceleration somewhat, at least from what I have read. If the total package is lighter, it would negate the effect somewhat of placing the greatest density, the actual rim, further from the center, where it will have a greater inertia. I have no facts to back this up, but it does make sense mathmatically, that if total weight is equal, moving the greater portion of the weight outward, will cause the total package to require more energy to spin it up, or slow it down.

The one advantage of pumping up the stock engine is it does not require any other substantial changes, like ECM's and different sensors etc.. The down side is, the total power output does not have the same potential as a boosted engine. You should be able to realistically achieve something around 200 gross hp, with basic hot rodding, which is about a 20% increase. You will feel that much of a difference. Parts to overhaul a Buick are 2-3 times as expensive as the equivalent Chebbie stuff, but the machine work is the same. A good used L67 engine, not requiring susbstantial work, is most likely less expensive, but has other issues. Different strokes I guess.

[padgett]

Just an observation. "Ford uses an equivalent injector at a lower pressure of about 36 psi in the 5 litre at about 19 lb/hr." Each cylinder of a 3800 V-6 is about the same size as a 5.0 V-8. No wonder they use the same size injector.

[Guest imported_lbowejr]

You wrote "I am running a 24 lb/hr injector @ 3.5 bar for about 26 lb/hr, which seems to be close to what the stock ECM can control."

Where can one find such an injector and does it just bolt right on or do you have to make mods? If mods, can you describe them? Thanks.

[2seater]

The displacement per cylinder was not what I was trying to illustrate, it is the flow rate at various pressures. Ford used the same injector in the 302 and the 351, at least in some vehicles. The design of that particular injector is wrong for our application, and what I am using is from a Corvette. Our intake is bored straight through so we cannot use the injectors with the little plastic "hat" on the end. I got mine from Sunrise carburetor http://www.suncarb.com/ They deal in reconditioned injectors as well. You could just push the stock injectors to about 4 bar, or 58 psi and get almost 22lb/hr, which should supply over 220 hp at 85% duty cycle. Personally I prefer to run the injector at a little higher duty cycle since they "dribble" badly when they open and close which is part of the reason if the ECM isn't designed for it, or you don't need it, a big injector is a bad idea. The only reason I have larger injectors is to try to supply fuel to the turbo engine. The stock injectors, and stock pressure, worked just fine even with higher compression, no cat. larger throttle body, premium fuel chip, CAI and hand porting of the intake and heads. Horsepower was estimated at between 195-197 and the injectors ran at just over 90% @ 5000 rpm.

[Guest imported_lbowejr]

2seater - you wrote " You could just push the stock injectors to about 4 bar, or 58 psi and get almost 22lb/hr, which should supply over 220 hp at 85% duty cycle." How does one change the injector psi? Sorry, I'm a novice.

[Guest imported_lbowejr]

Thanks everyone for the advice. I replaced the stock air filter box with a cone filter. I found a kit at NAPA that is designed for a Civic. I had to cut about 4 inches off the chrome pipe but other than that, if fit well. I can definitely notice a difference in performance. I already put a high flow cat and muffler but still have the 2.25" piping and have not ground out the blockage. Would you anticipate that I would notice additional performance by putting a 2.5" pipe and removing the blockage?

[2seater]

You need to have an adjustable fuel pressure requlator. The only reason to change fuel pressure would be to supply more fuel to match a substantial engine upgrade. If you do push the fuel pressure higher, it is a good idea to have a fresh fuel pump, as high pressure is harder on the pump than low pressure.

Opening the exhaust restriction is a good complement to helping the intake restrictions. The 2.5" exhaust would probably be a good addition also, but no larger. I have no experience with the larger diameter as mine boosts just fine with the stock 2.25", although I do not have a cat.

[Guest imported_lbowejr]

From your picture, it looks like you have a supercharger on the stock 3800 motor. Is the case? I thought you could not put a supercharger on the stock motor.

[poncho]

His motor is an "L" type, I believe.

[2seater]

It looks a little different now (old photo) but that is a turbocharger where the stock air box was. The engine is a '90 vin "C". The turbo is an amalgam of three different ones from the same family, the Garrett T3. There are now triple vents from the valve covers, no connection to the PCV system from the air intake pipe and the air filter now resides where the charcoal cannister used to be, outside the engine bay forward of the left wheel.