Topcat7

I am tossing up whether or not to remove the A.I.R. pump from my '89 L98 Corvette.
I am told that by doing so I can expect an increase of between 20-30HP. Is this so?

I am also told that there is a 'restrictor' in the air intake system that was put there to 'de-tune' the engine,
and if you remove that 'restrictor' you can make significant gains in HP by improving the air-flow. Is this true?

Red86Z51

You were told incorrectly regarding hp gain by removal of the air pump...the short answer is no.

Joe C

you would be lucky to see 2-3 hp. definitely nothing by the SOTP. removing those things seems like more trouble than it's worth.

Topcat7

Thanks @Red86Z51 and @Joe_C . If that is the only gain, it is not worth the cost.

Does anyone know about the 'restrictor'?

Joe C

been into C4's for about 25 years now, and can't recall anything about a restrictor. the air intake is somewhat restrictive, and there not much that can be done with stock components. gasket match, a little pocket porting, and long tubes is about all you can do to a stock system. L98's are L98's - more torque than horsepower.

Red86Z51

The ONLY restrictor I've ever known of in the L98's is the restrictor in the rear coolant passage of the intake manifold... that's there to keep coolant at the rear of the engine a little longer. Removing that would do nothing for your engine's performance...removing that simply allows you to remove that small bypass hose that runs to the coolant return line from the heater core.

Tom400CFI

X3.

The only "restrictor" that I'm aware of is the entire TPI system.

Paul Workman

As mentioned, there's little if any meaningful performance increase as result of removing the A.I.R. pump. However, removing the pump can negatively affect the efficiency of the cats - especially on start up, not to mention having to pass the smog station inspection of factory emissions equipment!
Restrictor plates apply to certain racing rules (NASCAR, etc) intended for "normalizing" horsepower of all competitors. Such restrctors in reference to the standard (i.e., street driven) cars is pure internet BS.

belairbrian

My 92 had the restrictor, but I got tired of hearing "slow your a$$ down", so I removed her it..

pologreen1

While you are at it...

All smog items, ac, and heat, radio, speakers, frisbee, spare tire, cruise control, stock exhaust, etc. The car will feel a lot better. j/k.

The car is a detuned 350, that is done with emissions, excessively restrictive intake, exhaust, heads, small cam, ECU,

A good running / breathing "hypo" 350 on pump gas is capable of 425ish chp. Basically you heard right. It is choked.

LT1 intake
Heads
Cam (if auto need stall / gears)
Headers/ exhaust
1.6rr's
24+lb injectors
Tune

So that recipe will get you some where around 425ish chp. Pricey though!!!

aklim

But if he has no emissions to pass, it should be fine. More room to work around in the engine bay is a good thing. Does smog testing do a cold start up test?

Tom400CFI

No. Can't test anything until it goes into closed loop.

LWesthaver

I removed my A.I.R. pump and I noticed that the engine compartment was a lot quieter when the engine is running. I never realized that the pump made so much noise.

But the main advantage is having more access to the front of the engine. The water pump in particular. There's a lot less clutter on the front of the engine now. And you loose about 15 pounds of hardware and plumbing.

-Wes

aklim

Was your pump broken or not working well? Mine was and it did not make it much difference, noise wise.

85WHITEZ51

The only other benefit I'm aware of that hasn't been mentioned yet is it gets it away from from your alternator a bit. I've recently done this mod for this reason as I'm getting tired of fried alternators, but since I just recently did this I can't personally confirm it helps but it did move it away from my headers.

Topcat7

Thanks, Guys. From what you have said, I have decided to leave the A.I.R. pump where it is, (at least until I decide to install headers).

As far as the 'restrictor' goes, if there is not one to remove, then I cannot remove it.

Actually the car performs better than any car in my (small) collection as it is, so I think that I will just be happy driving her as she is.

Thanks, again.

aklim

What has the AIR pump got to do with the alternator? It doesn't even get that hot.

aklim

At which point, you can run a pulley to delete it.

Of course there is. Intake. Tune and headers with intake would be great

LWesthaver

My smog pump was making (what I believe was) bearing noise. I never noticed the noise until it was gone.

aklim

Ah. Like I was saying, but in a clumsy manner, my pump was ok and I didn't notice much sound change after I took it out. It did spin freely.