I've got the intake off right now, and have been wondering if I should do a TB bypass. What are the advantages and disadvantages of doing this?

 

Mostly, it's to "clean up" the engine compartment. Coolant is routed thru the TB to prevent icing in extreme cold (30-below or something like that). If you're like most people and don't drive your vette much (or at all) in the winter, there's no need for the "option".

Some would suggest that the TB-bypass also helps power by removing a source of heat for the incoming air. Normally, you'd want the (incoming) air as cold as possible to create power. But there isn't much concensus regarding the validity/amount of gain. IOW, don't plan on it registering on a dyno.

FWIW: I cutoff and created an extra clean, polished IAC housing sans the coolant ports. One of these days I'm putting it up for sale in the parts forum. (I had two to work with when I built my 383. Both turned out well). Still trying to decide fair price.

Here's how nicely you can remove the water tubes....

 

Thanks gregg. So it's pretty much pointless either way?

 

Right, pretty much pointless unless you live in Alaska. Less to leak and Greg is right, really helps clean up the engine compartment.

 

I just went through the same process you are. Bolting on the intake and debating on the TB cooling hoses.

I totally agree that not hooking them up really cleans up the appearance, may not have any adverse effects at all and a PITA to connect but...

If you have an operating EGR system on your engine, hot exhaust gas is getting routed up to those two holes on the bottom of the upper plenum right behind the TB butterfly holes. That exhaust gas is going to make things really really hot over time (long drives for example) and the incoming air is going to be heated more than it should. The TB cooling chamber is not there to heat the TB but to cool the TB at this point. If you're not running an operational EGR system I'd definitely leave them off.

(others on this forum have already called me crazy and stupid for considering this possibility but because I have an operating EGR, I hooked up the hoses as the GM engineers did).

 

C4Betts, I made a block off plate for the EGR. There's another question, since I deleted the EGR should I also get rid of the pipe that goes to the manifold? I left that on because I didn't see a way to weld up the hole where it clamps to the exhaust manifold. Is there any other way to do this?

 

Make a blockoff plate for the riser flange on the exh manifold and remove the EGR crossover pipe to the intake
Buy a #10055726 gasket and use that as a pattern for the plate
http://forums.corvetteforum.com/c4-t...post1576783419

No need to seal rear EGR port on intake except for cosmetic reasons because your EGR is already blocked by the plate you made for valve

 

And as previously explained ; EGR gases only flow under certain conditions as programmed in the tune
There is not a constant stream of hot exh gas flowing through the plenum

 

Mine is an early model that clamps on to the exh manifold. It doesn't look like it bolts on.

 

but...I don't particularly care for the cleaned up look unless you modify the IAC housing and remove the hookup tubes.

Add me to the list of people who think you're wrong. The EGR is used to dilute the incoming oxygen when combustion temps get too hot. The EGR doesn't make things hotter, it cools them down. It may not make sense but consider that incoming air (thru the TB) is at least 100-degrees cooler than the intake. (No matter what the temp outside, it's cooler). When the incoming air hits the EGR gases, they mix and cool. There may be a slight elevation in the intake around the EGR passageways, but there's no way that's going to have an appreciable affect on the incoming air charge. In fact, I think you're ignoring the much greater impact of the incoming air.


Also: Combustion temps are cooled to eliminate NOx gases as a by-product of running new engines hotter. Engines are purposely run hotter to create more power and burn cleaner. The bigger the differential between incoming air and combusion temps, the more power you get. (That's why people like to run 1/4m when it's cooler outside.) Higher operating temps also flash-burn the fuel better for lower emissions (except NOx which the EGR addresses).

I think the EGR should be left in tact for those not altering their running temp. If you're modding to get more power AND lower temps to prevent detonation (or for some other reason), then go ahead and delete the EGR.

But that B.S. hose pumping coolant thru the base of your TB is a wasted piece-o-crap.

 

GREGGPENN, excellent points with good supporting rationale. I can get behind that and agree with you.

 

On my 92 the tb coolant hose has nothing to do with the EGR. BTW your EGR is only functional at idle rpm's.

 

Removing the cooling hoses now means that you can take the throttle body off quickly without getting into draining coolant and burping rads later on too. I think the actual icing occurs when it is just above freezing, air is humid still and the rushing air cools the body to below freezing, but still, not likely going to be an issue.

 

Cool!

The other thing I forgot to throw out there is the coolant routing itself. If this feature was really designed/needed to cool the TB (or other areas of the intake), I would think an internal circulation path (like the coolant thru the block) would be needed.

Since the coolant only has a small chamber, inside the IAC housing AND under the TB, it seems likely that heat rising would help "defrost" the blades above. But, there's not enough evidence of circulation pathways to affect overall component temps.

 

EGR "operates" at cruising speed,not at idle.

 

Correct, EGR should be open at part throttle/cruise and closed at idle or full throttle.

Exhaust gas being fed at idle causes huge stumbles and misses

 

I can see you two becoming best buddies working out conspiracy theories nobody else has given any thought to

This was explained to him in his other post but he liked his theory better

that bypassing the throttle body coolant chamber could possibly hurt performance by this area actually getting much hotter without it due to the hot EGR gases

 

makes it easy to pull the throtle body off next time,only advantage

 

Wrong. At the track, some racers will ice down their plenums and throttle bodies to try to lower the intake air charge temperature. A lower temperature charge will be a denser charge and will hold more 02, which, with the proper fuel mixture will increase horsepower. That is the premise of having a cold air intake. Colder air from outside the engine compartment enters the motor and increases hp. If the throttle body is heated to 200+ degrees, the air charge is warmed up slightly as air rushes through the throttlebody opening and hp is lost. A warm throttlebody acts as an air-air heat exchanger. I monitor the intake air temperature of my SuperRam manifold during every pass and I can see with timeslips the difference between a hot intake vs a cooler intake. Picture of my car with the throttlebody bypass...