it's probably been discussed before but ayways. as far as I know, the coolant line through the throttle body is used to keep the butterfly from freezing in winter. So it's actually a throttle body heater.

Is it just me or raising the IAT isnt something that we want? assuming I only drive in summer so I could care less about butterflies freezing, would bypassing the TB help lower the intake air temp at all? it's a pretty cheap and easy mod

 

http://www.rx7.org/Robinette/throttle_body_coolant.htm

 

Is there a more useless mod on a street car?

 

Not if you end up having to pull the throttle body or UIM off a few times - say to get to vac hoses, fuel injectors, or those annoying coils. It''s nice not having to worry about spilling coolant everywhere. On my next engine, I'm having those two nipples that feed the line removed and capped.

 

bypass the coolant...better yet, remove the butterflies. Gains? minimal but it'll give you something to tinker on. On the lsx engines people do a TB coolant bypass mod too. Again, probably doesn't do a whole lot but I guess every little bit counts.

 

I remember a mechanic we used to have at Gotham telling me the Firebird/Camaro guys used to report gains of up to 5 rwhp by deleting the coolant through the TB.

 

Time out.

When you remove the coolant hose, you disable the mechanical cold idle system! Think about that before you pull it out. I have actually reversed a TB coolant hose delete, I got so annoyed by the unstable idle and keeping my foot on the gas. Another minor issue is that if you ask somebody (family member, a carwash place, wherever) to start your car up they will have no idea what's going on if it stalls or runs rough.

Service highlights document page F-19:



One coolant hose isn't going to conduct a ton of heat into the intake charge. Heat has to conduct from the coolant to the hose and to the TB itself, and then from the TB metal to the intake air. Who detonates because of the factory coolant hose? I run that hose on my single turbo setup and a friend's stock twin setup with no knock or any other problem. And 5 hp? What are you driving, a Civic? You can gain 5 hp just from the ambient temperature dropping a few degrees. Check uncorrected dyno numbers on different days and you'll see what I mean.

Some of those other cars run a similar coolant hose to maintain a relatively fixed temperature to a drive-by-wire actuator (Rx-8 for example) or ISC valve (2nd gen Rx-7, which also has a mechanical fast idle system using TB coolant). These systems use the coolant to maintain longevity of those various air-related solenoid valves and for driveability in more extreme weather conditions. They often have stepper motors controlling idle air and deleting the TB hose doesn't make a difference, like on LSX engines that are not drive-by-wire.

Is one hose that big of a deal? Yeah it's annoying, but when you figure out the trick it's not so bad to remove/install.

 

When I cold start my FD, the idle sits right at 1000 rpm and isn't noticeably rougher than usual. Same thing for the customer cars that we delete the coolant thru the tb. I think it comes down to tuning, as well as having a fresh throttle cable and having all of the tb settings adjusted correctly.

I should say we delete it on most single turbo performance builds, for near stock cars or conservative/older owners we tend to leave the system as-is.

 

^ Are these cars retaining the ISC? What is their warm idle speed? I don't think it's a good idea for the OP to eliminate something when he doesn't even understand what it does.

 

it's not that I don't understand what it does, I'm just wondering if it has any benefit at all

thanks for the answers, I should hav checked robinette before asking

 

Yes, we retain ISC on all cars. That is one of the few things I don't like to delete . warm idle speed varies, typically with the street port they're anywhere from 900 to 1000.

 

I already have the fast idle cam removed. I want to do the coolant bypass. If I remove the warm up plunger, is some kind of bop needed to seal it off? Do you just cap off or the gold colored hose barb, or is there a way to actually remove it? What about down on the bock, is that just capped?

The big hole on the bottom left of the single place is for idle, correct? It looks like a passageway that continues on through the extension manifold.

 

I think typically people just run it back to the waterpump .. so it'll still come out the back of the block and will connect back up to the 90degree tube on the waterpump housing.

You don't need a BOP for the TB.