girvan

Here’s a simple yet effective way to get a few more HP. The throttle body on the GS400 and I’m sure most other recent cars is water heated. This is to achieve very low emissions, avoid throttle icing and make the car more drivable in really freezing starts. Since I live a temperate climate, these issues don’t worry me.

What I did was to block the heat. This reduces the air temperature and allows denser, cooler air to enter the combustion chambers. A secondary and possibly bigger advantage for cars in California is that the knock sensors do not back off the timing so often due to 91 octane gas combined with a hot air. I can feel quite a difference. I have noticed in the past that the car has more power before the temperature gauge stabilizes.

Although I have not been able to measure the difference or photographically document what I did, but I wanted to pass this on. This is a well known technique to get more power. These Corvette tests are very scientifically done with 6 HP gain:

http://www.ws6.com/mod-8.htm

I believe the gains with CA gas could be more. I’m not sure what the knock sensor recovery strategy is in these cars, but on some GM cars, the timing is locked to a more conservative curve until the next time the car is refueled.

The throttle body on a GS400 has its very own hot water feed branching just before the main thermostat on the engine block. The pipe is connected to the base of the throttle body through a second miniature inline thermostat labeled 93 degrees C. I opened the large hex plug on top of the throttle body and plugged the lower coolant passage with a conical rubber plug. It is firmly wedged in place by the replaced hex plug. I used a rubber cap made to cap vacuum fittings. Other possibilities are to remove the coolant hoses and inert a blocking object in one or clamp one. They are a little awkward to get at and the input and output are different sizes so bypassing is not an easy option.

Again sorry for no photos or power curves but maybe others have the time or resources to document this.

tomtnc

I blocked off the throttle body coolant lines on my Z28 and Corvette...worked like a charm with no ill effects.

Some foreign cars read the temperature of the coolant in the throttle body as a parameter to determine idle rpm (mazda KL-03). I'm assuming since you haven't had any problems with idle rpm, this is not the case with Toyota.

This is a relatively easy modification and improvement results have been well documented in various makes/models of vehicle. I'll probably try this mod on my car very soon and compile a DIY.

If you wanted to take this theory a step further, you could make a phenolic throttle body gasket to mount between the throttle body and intake manifold. This would significantly reduce heat soaking from the engine to the throttle body. Same could be constructed for the intake manifold gaskets.

DaveGS4

iTrader: (2)

You can pick up the phenolic gaskets right next to the dilithium crystals in your local auto parts store.

tomtnc

ROFLMAO

Mean Gene

Dave - Didn't U change your dilithium crystals when U rebuilt your warp drive? Personally, I like the gasket-free flux capacitor molded into my SRT intake!!

BananaGS

I was gonna do this a while back, but decided not to,
this coolant by pass thingy is the oldest trick in the book. The proper way is to bypass the coolant line going in/out the throttle body. basicly connect the input line to the output line w/o going through the throttle body.

what is the side effect? possible rough idle in the morning especially for those that live in the cold section of the town, the whole idea is to warm up the intake air when it is cold outside for a proper idle. But when your engine is warmed up, this thing keep heat up the air more -> that is why you may gain some power by bypass this line. Don't try to block the line.

girvan,
how long have you had this setup? idle is still good? I may give it a try sometime next week, since Lexus could not fix my low idle problem, I am gonna try to fix it my self, while I was at it, I will by pass the coolant line also. Does your dyno butt feel any gain? hee hee


Anh

PAULGS430

mean gene is the flux capacitor under the warranty? I would also like to change the speed of my quantum level oscillation delay of the SRT intake.

Paul

BananaGS

here is a picture that I took the last time I was thining about doing this.

another REAL power is light weight drive shaft, carbon fiber drive shaft should give another 30HP or so, hee hee, get you close to that GigaWatt, 55mph back to the future speed.

girvan

Banana, I have tried the mod for over a week and 300 miles, town, country, freeway, mountains. I have colder Denso Iridium plugs (IK22) than the OEM NGK Iridium’s for a year so my engine is even more sensitive to idle problems and I have had none.

My way of doing the mod DOES block the coolant line just as the Lexus inline thottlebody thermostat does when the temperature gets to 93c. That is not a problem. Bypass may be just fine too - It's a small "short circuit" of the water pump.

I can definitely feel a gain. More curious is that part throttle kickdown is reduced, a characteristic I prefer especially as I have e-shift to override this. It must be something related to the ECU seeing a lower air temperature.

GSquicksilver

girvan, so you mean with the Denso plugs, the engine actually idles rougher than with the NGK plugs?

girvan

Sorry for confusion: The engine idles perfectly with colder Denso plugs. The engine also idled perfectly with the OEM NGK IFR6A 11 plugs.

I changed the plugs to one step colder as I have done in every car I have ever owned. Although plugs are a physically small part of the over all induction tract, they have by far the greatest influence on charge heating and pre-ignition. Plugs are normally spec’ed for worst case 150k miles engine wear and 30 minutes idling performance. The point is if my car has no negative effects with cold plugs, cars with OEM plugs are even less likely to have an issue.

SCV8

That's a good mod,when people pay $1000 for an ECU upgrade,a plugged off coolant line for 4-5 hp is a pretty good deal.
Machining that phenolic is a hassle,might try that later;thanks.
I guess that's what makes the difference between a "bolt-on intake",and a well engineered,truly custom mod,it's for those who know.

skier1

Bwaaaaahahahahaha! I just pulled off my throttle body, cleaned it out, and bypassed the coolant line. Very easy to do. Now the car idles perfect in drive without the air on.

Oh, by the way, I replaced my aging dilithium crystals and cracked phenolic gaskets while I was in there! My flux capacitor was OK and fully charged!!!!

hee hee

girvan

Banana,

In your picture a few posts above you have the cover (held by two Philips screws) of the air passage above the throttle removed. I assume that was intentional? You will see about 20 tiny holes that suck air only at idle to bypass the throttle passage. Perhaps these are gummed up with blow-by gas and giving you the bad idle?

BananaGS

In your picture a few posts above you have the cover (held by two Philips screws) of the air passage above the throttle removed. I assume that was intentional?

oh, I had opened it out to clean it, when I took the picture

---------

skier1, what did you used to join the line? I know the lower pipe is 3/8" and the upper pipe is 5/8"
I found a gas pipe that has this set up but i did not do the mod yet, i was waiting for my service manual to see if lexus had put some special water gate or anything in the line, =)

Anh