Throttle body coolant bypass?

[NY Pete]

Now, I'll preface this by saying I don't have my Vibe yet, but I just recently read the SAE technical white paper on the design of the 1.8L 1zz-FE Toyota motor. I noticed that it showed a cooling system schematic that appeared to have coolant running through a chamber in the throttle body. Can anyone confirm this? What's more, if it exists has anyone bypassed it? I know back in the day it used to be a cheap little mod we did to LT-1 and LS-1 V-8's which kept the intake air temperature down a bit (especially in the summer). The only reason it's there in the first place is to reduce start-up emissions by warming the intake air charge in cold weather...any comments?

[d_m_kolb]

I have done this to my 2001 Kia Spectra. Very easy and it's a free mod. It will help keep intake temps a little lower but this mod should be combined with a thermal intake manifold gasket to keep the head from transfering heat to the intake manifold and also a CAI.

[PBFlash]

How much HP will bypassing the throttle body coolant get you?What about the thermal gasket?How much is the gasket?

[d_m_kolb]

This mod by it'self would give you very little HP gain. It needs to be done with other mods.Here is info on the Thermal Gasket.http://forums.genvibe.com/zerothread?id=1104

[XRSizzler]

Actually, for a street driven car, bypassing the TB would hurt performance since the coolant is designed to cool the TB due to heat input from EGR gases being recirced in to the intake for emmisions and higher combustion efficiency. This only happens during cruise conditions. The bypass may be benefical during WOT drag racing with a relatively cool engine. Believe it or not!If you disable the EGR, then you might loose cruising fuel efficiency and advanced timing during light throttle since the ECU uses this input plus others for A/F calculations.Mo

[d_m_kolb]

No that isn't how it works. You would think because coolant is flowing through your intake manifold that this would help keep the intake manifold cool but 200 to 220 degree coolant flowing through a intake manifold doesn't cool it at all. It raises the intake manifolds temp a lot.

[XRSizzler]

How hot are exhaust gases? These are the same gases that come from the cylinder head chambers that are recirced back into the intake. They're about 1000-1400F so the relatively hot engine coolant at 220F will cool the TB. They may have cooled to about 500-600F by the time they hit the TB and intake. The exhaust gases are designed to be a "quench" gas...During cruise or vacuum conditions, the EGR valve WILL open to allow hot exhaust gases to enter the intake. The EGR valve is only shut during WOT (no vacuum) and cold startup conditions.Mo

[d_m_kolb]

If I'm not mistaken EGR valves haven't been used on engines since 95. Yes your right that the head gets very hot. Coolant in this area of the engine passing through the head heats up to well over 260 degree in some areas before returning back to the radiator to be cooled again.Where the intake manifold contacts the head of the engine is going to be very hot unless you have a thermal spacer. Now the begining of the intake manifold where the throttle body is attached is going to be much cooler than where the head and intake meet. That area of the intake manifold will be cooler if hot coolant isn't runing through it. On my car coolant runs first through the throttle body and then to the intake manifold. I did the old put your hand on it test before and after this mod and there is a difference in temp. It's cooler close to the TB. It seemed to be cooler buy the head as well. My CAI increased this effect once I had it in place. I'd like to install a thermal gasket and the entire manifold should stay very cool but I haven't done this yet.

[NY Pete]

Well, I've never heard of this "thermal gasket" stuff anywhere else, but I can speak on the fact that the 1zz-FE in fact DOES NOT have an EGR system (as Admin II just noted).And as far and the coolant path in this engine, it appears it flows from the block to the cylinder head to the heater core, throttle body and radiator (there are two ports coming out of the head, and the one to the raditor is a "Y"ed out to the radiator and throttle body). Assume that coolant temperature is very high at this point and most likely only beneficial to start-up emissions...

[XRSizzler]

I have to agree this ia a very controversial subject with bypassing TB coolant passages. I think it is safe to assume without me looking for the EGR valve on my XRS that EGR operation is vital to emissions standards or reducing NOX, nitrous oxides emissions which occur in combustion chambers greater than 2500F. Without recirc of this 'hot' quench gas, NOX will soar above acceptable levels. You will not pass any smog test w/o it. Having said that, the Matrix/Vibe and all modern new cars will have EGR systems. Most EGR systems/valves will be cooled by engine coolant. This exhaust gas is considered inert or not reactive with anything. But, it will carry heat to the intake, as you know excessive heat will car gas expansion and therefore lower power due to less oxygen density.What I'm trying to say is bypassing the TB coolant may only be beneficial during periods of no EGR operation, ie during heavy load (WOT) or no vacuum. Other conditions include idle and cold startup. No hot gases are allowed by the EGR valve. But most people are usually in the cruise mode.If you have a thermal spacer between the intake and cylinder heads, it may allow less intake air heatup during drag racing or WOT. But the downside is less heat rejection via the mass of the intake to ambient therefore more heat is contained in the engine block so the engine coolant system has to accept more heat blocked by the thermal spacer. This may tax your coolant system and allow you engine to run hotter negating the spacer gains.Some of these tricks can work mentioned above can work under specific conditions but most do not for street cars during cruise or closed loop conditions.Sorry to be long and winded

[d_m_kolb]

There is no EGR system on new cars. The coolant bypass would help at all RPM once the engine was at normal operating temp. The thermal gasket which is made of of G-10 phenolic material (and doesn't conduct heat well) blocks a lot of heat from transfering from the head to the intake manifold. http://forums.genvibe.com/zerothread?id=1104 Once the manifold is hot it transfers heat to the air reducing HP. Cooler air is densor which means the cooler the air is that reaches the combustion chamber the moreair reaches the combustion chanber and the more HP you'll make. If that air is heated up it loses some of it's density. The coolant by pass keeps the HOT engine coolant from running through the cooler intake manifold there for not heating up the intake manifold as much as if the coolant were runing through it. This means the incoming air will be slightly cooler.

[NovaResource]

XRSizzler,First, there is no EGR. Read it here in the following technical bulletin on the 1ZZ engine (see page 8 under "Clean Emissions"): http://www.matrixvibe.net/docs/1zzfe.pdfSecond, coolant is passed through the throttle body to keep ice from forming around the throttle butterflies and sticking them open. It has nothing to do with emissions or cooling the intake and throttle body. Unless you live in Canada or in VERY cold climates, you probably don't need it. With this mod the engine will start fine, but it will idle a little lumpy until the engine warms up. Air inlet temperature is only SLIGHTLY reduced at best by this mod.Read here for more info:http://www.frankhunt.com/FRANK/corvette ... pass.shtml

[XRSizzler]

Ah, does the 2ZZ-GE have EGR function? If not, I stand corrected and thank you for your patience during my babbling. If it does not, then it is an engineering marvel to keep NOX low for an TLEV rating. I'm assuming this must be done with a combination of a richer A/F ratio and some how keeping combustion chamber temps well below 2500F.The catalytic convertor also must also use Rhodium as a catalyst to keep NOX down but would be expensive since it's a very precious metal with limited availbility.It's hard to believe the hot coolant purpose in the TB is to keep it from freezing. There must be disimilar metals used in the TB to cuase different contraction and expansion rates to make sticking a liability???Any stuck open throttle would raise an eyebrow!Anyways, this thread has been very imformative for me, i'd like to see more

[NovaResource]

No, the 2ZZ-GE doesn't either. Did you even read the Technical Bulletin? It says:quote:CLEAN EMISSIONSThe intake and exhaust systems are laid out in reverse compared to a traditional layout so that the exhaust manifold is located at the rear of the engine when it is in a front-engine front-drive vehicle. This made the distance between the engine and the under-floor converter shorter and improved the warm-up performance of a converter. Thanks to this exhaust system layout, the under-floor converter has the same warm-up performance as the manifold converter which has traditionally been located on the front side. Instead of the conventional two-hole injectors, the new engine is equipped with four-hole injectors which are capable of atomizing fuel into even finer particles. The injector is mounted in the cylinder head, thereby reducing the distance between itself and the combustion chamber. This helps prevent fuel from adhering to the wall surface at the intake port, thus reducing HC emissions and improving fuel consumption. This arrangement has made it possible to comply with the U.S. TLEV emission regulation without using a manifold converter or a start catalyst and elimination of the EGR system was also made possible. At the same time, it has enabled us to cope with future regulations which will become even more stringent.The heated throttle body is not because of "disimilar metals" or "different contraction and expansion rates" it's because air rushing through the throttle body can create ice on the throttle blades and stick them open.

[d_m_kolb]

Anyone wishing to do this mod I have taken a few pics of mine to help explain how to do it.In this pic you can see the inlet and outlet nipple where the coolant enters the throttle body runs through the intake manifold, and then exits out the other nipple in the throttle body. There was a hose attached to both nipples. (Two in all) You'll want to take one hose completely off. You should now have no hoses connected to the inlet and exits nipples of the throttle body. This leaves you with one hose attached to your cooling system and one nipple on the cooling system still open. Take the hose and connect it to the nipple with nothing on it. What this does is just sends coolant through the hose and back into the engine totally by passing the throttle body.It should look something like this when complete.

[andrewmva]

Old trick!!! I did it on my 90 honda prelude..... I did not really feel any difference.... -but who knows.... be a nice sunday project anyway....

[DABEAR95]

quote:If I'm not mistaken EGR valves haven't been used on engines since 95. Yes your right that the head gets very hot. Coolant in this area of the engine passing through the head heats up to well over 260 degree in some areas before returning back to the radiator to be cooled again.Where the intake manifold contacts the head of the engine is going to be very hot unless you have a thermal spacer. Now the begining of the intake manifold where the throttle body is attached is going to be much cooler than where the head and intake meet. That area of the intake manifold will be cooler if hot coolant isn't runing through it. On my car coolant runs first through the throttle body and then to the intake manifold. I did the old put your hand on it test before and after this mod and there is a difference in temp. It's cooler close to the TB. It seemed to be cooler buy the head as well. My CAI increased this effect once I had it in place. I'd like to install a thermal gasket and the entire manifold should stay very cool but I haven't done this yet.They still use EGR valves on engines, it just depends on the engine and its design. I know camaro's had EGR valves in 1997. I'm not sure about 98+ and the LS1 engine. My 2002 Golf has an EGR valve. It has allot to do with the ability of the catalyst to warm as already mentioned, and also the design of the camshaft. If the cam has "enough" overlap an EGR valve is not necessary.