hey guys, I did the TB coolant bypass but my TB is still hotter than hell after I drive the car. Is it supposed to be "cool to the touch"? How hot do your TB's get w/ the bypass mod? I cant touch it for more than 2 seconds....ouch...i still feel the burn

Due to normal convection, the throttle body will pick up heat from the engine. The purpose of running coolant thru the TB was to prevent throttle icing in cold weather conditions. Removing the coolant lines from the TB, IMHO, does not do a thing for performane, as heat from the engine will keep the TB just as warm as the coolant.........

My TB did feel cooler after I bypassed it...Also, it is 2 less coolant connections that could leak....

That is how I justified it...

I am gonna do it just because the U-Hose is half crimpted buy SS fel lines that were dona up wrong... My heat is not that hot and I think it is from retricted flow.

When I did it, I could definitely touch the TB. I hook it back up in the winter though. It gets pretty cold here and the last thing I need is ice on the TB blades.

hmm...do you guys think that maybee some of you (the IROC's in particualr it seems) may have aluminum throttle bodies...or some other material? I know mine sure as hell isn't aluminum b/c the heat it gives off is ridiculous!! Just a thought b/c there is no way in hell some of us are running cooler and some of us arent if the TB's are the same metal.

Those that aren't feeling a difference in temperature: Are you stil running coolant lines from the TB to the underside of the car? You still need to do this because air is forced through the lines and the cooler air cools the TB down. Otherwise it would still stay warm from convection as mentioned before. I run one of the lines behind the headlights on the passenger side on my Iroc and the other side I just route down. This way you get airflow through the hoses. Just checking to make sure you're doing this in addition to re-routing the coolant.

I live just south of 90Iroc (Franklin, IN) and did the TB bypass three years ago. I've never had any problem with icing (yet), but never really noticed any difference in performance from doing the mod. My TBs are both aluminum (stock and 58MM) and would scald my hand if I touched them before the mod. After any extended period of running, it is still hot even with it bypassed, just not as hot as it was before.

Sparks a flyin'

I did the TB bypass and the TB now stays cool enough for me to rest my hand on it right after driving it. The air flowing thru the TB keeps it that cool. If I let it stand for more than a few minutes after driving it, then the TB gets just as hot as it would without the bypass because of heat rsing from the warm engine. As far as any gains in performance, it helped get rid of a low end bog around 1200 rpm in hot weather.

actually looked into this subject quite extensively. talked to my bro-in-law who is a private pilot and flight instructor. he says that iceing can occurr at any temp between 40-70 deg. fahr. makes sense if you understand air and fluids when pressure changes occurr. when air flowing undergoes a pressure change as in a carb. venturi or throttle body it will rapidly cool and depending on rel. humidity ice could happen on a seventy degree day while sitting traffic. when air is flowing into the plenum through the throttle body the body stays relatively cool. as pointed out after you shut off engine thermal conduction from intake and block will transfer to the top of the plenum(acts like a heat sink). for the record i would NOT recommend bypassing the throttle body warmer. the performance does not change and you would well run the risk of an iceing problem when conditions were right. my sportbike has carb heat and i took it off, it NEVER ran right after that. idle speed would change depending on engine and ambient air temp. always remember one thing, the engineers would not install it if it was not needed. Danno

Hey Danno, that's good stuff man...and you are absolutely right actually. Goodinfo...thanks....LOL, i took fluid mechanics and all those engineering classes a while ago. LOL....looks like I wasnt paying attention much ehh? LMAO

about a week after i did the TB coolent bypass mod. i broke that heater control valve that used to connect to the TB. when i connected the valve to the block, it was at more of an angle since i used a single piece of rubber, and anyways it was too much of an angle for the plastic valve peice and it broke spewing coolent everywhere, replaced it and i think its leaking again.... time for an elbow piece now i guess..

To the guy whose hot water valve broke. I actually did the mod when first read about it. Had the same thing happen. Suggest using new hoses to the valve(the ones on top of one another). Cut them AFTER you move the valve foreward to compensate for the difference in the bypass hose angle vs. stock position. One hose will come from htr. core, other on my 89 iroc came from below off a metal line. The new hoses will be a little longer, and also newer rubber will be more supple and conform itself in time. Good Luck. Danno

Not to be a lone voice of dissent here, but I think the coolant bypass mod has its definite place.

1. I have a 406 in my car and it produces enough heat so that I am sure I will not get icing in spring, summer or fall here, at least it hasn't happened yet.

2. I don't drive my car in winter or when the temperature is below 50 degrees. I am willing to risk icing for the decreased intake air charge temp.

3. It is another point for coolant to leak. I removed that connection as well as that stupid plastic heater valve assembly. It simplifies things immeasurably. If you have to have a shut off valve, install a metal one from the auto parts store.

4. GM installed it because they realized that people would drive the car in any conditions, including 10 below zero in winter. If you drive your car in winter, then by all means, leave the coolant line hooked up.

5. Not to wonder here, but "carb heat" on a motorcycle (2 stroke or 4 stroke) isn't quite the same thing as my 406 with TPI. Sure, general principles apply, but real world experience tells me that I haven't seen carb icing on a 70 degree day idling in rush hour.

JMHO,

Here is another benefit of the bypass. You can take the TB off and on without having to drain engine coolant every time. Makes thing alot easier with the bypass. Less coolant connections, less chance for leaks.
Just need to get a piece of hose with a 90deg bend in it, so you can get over to the heater valve and connect up to it without forcing it a certain way.

As far as the temps, I didn't really notice the TB being much cooler. Never really monitored it before the bypass either. I can understand why GM did it. I don't run my car in the winter either. I do like the idea of getting rid of that heater valve. Got to think about that one.

Anything that you can do to help "clean up" engine compartment, the better off you are. My cold-start valve is hitting the road soon.

Just my 2cents.

Actually. I think I was the lone voice of dissent. Didn't mean to start a ruckus. The analogy with the bike is actually on target. Honda runs coolant thru the carb body just as our cars. When I took the heat off the bike I would be sitting at a light and the engine simply would shut off. Three other super hawks we did acted the same way. Funny thing was my iroc was bypassed at the time with no problems. That started my looking into the purpose of the heat to the carb. I ran into a factory Honda guy at a race and he explained that the idle air port was most likely icing up. I explained that it was eighty degrees and he said it did not matter. At idle the air intake is very small and the pressure difference is high which makes icing very likely and it in fact did happen, I would stop a run with the bike and watch the idle speed slowly drop and it would eventually shut off. I have talked with a friend who is a field engineer with Chrysler and he has pretty much said the same thing. I ran my rock with no problem in the time it was bypassed. I only meant to explain a little why the heat is there. I believe the formula is Pressure x Volume= Temp. Always enjoy the opinions on the board- Danno

I can appreciate the info though. I can see how it could work with an air-cooled bike, but with headers and my 406, I have heat pooling at the top of the hood, keeping my TB well above freezing.

Maybe on a bone stock 350, it could make a difference, but I don't think so. There are a lot of things that GM has done on the original configuration to be able to run the vehicle in varying climate conditions, from dead of summer to dead of winter...A potential 130 degree temp difference!

Anyway...don't worry about the ruckus...and who knows, I may get icing someday and vindicate you after all...but until then....

Adam you talked me into trying it again. In Pennsy here weather man said single digit wind chills. Pulled TB to clean and left heat OFF. So far, so good. Anybody notice K+N filters not as good as stock as far as dirt is concerned? Seems TB gets dirtier faster. Point of reference, my cycle is fully liquid cooled. Most of higher HP bikes are now all water cooled. I think Harley is about the only one still making a large displacement air cooled engine, and that will probably change. Log me out as ICEMAN. See Ya!

i have never seen so much contraversy over tb bypassing although it does seem to raise questions everytime. oh as for air cooled bikes most are V twins, H.D. Victory, Beul, Indian. but thats off subject right.

i have bypassed several cars and run a bypassed car in snow/ice whatever and never had a problem. theory is 1 thing the real world is another. my mostly stock 89 iroc with a 350 runs much, much cooler after i bypassed it. if i compare engine running with the bypass and without the tb and plenum see a major heat change. even after the motor has sat for a minute or 2 with the hood up now and i can still see a major heat difference. maybe its just me, but i doubt it, when i was working under the hood before i couldnt rest my hand on the tb or plenum without burning it, now i can rest a hand there all day.

oh and yes my tb is aluminum as they all should be, use a magnet and do a test to see if its aluminum or not. if it sticks its not, if it doesnt it is. but you should be able to tell just by looking.

with K&N's my tb has stayed nice and clean for several months now, i pulled the tb off and dismantled it for a good cleaning months ago. checked it on sat and it still looks great.

Danno, maybe the dirty appearance of the TB is either too much oil on the K&N or it isn't sealing quite right.

As for the bypass, I would love to hear if there are any problems with it coming up. In a way, this discussion is similar to removing the MAF screens. They are obviously a flow restriction (see TPIS insiders book) and yet people swear that removing the screens will cause the MAF to fail...isn't that what you have an air filter for in the 1st place? Either that or they have an older MAF sensor that is due to die anyway. I will find out in a few months and report back to the board.

I yanked my screens awhile ago and havent had a problem. my stock maf is slightly damaged around the sensor connection anyway so i figure even if it did/does die no biggie since i want to replace it anyway. but as it turns out it has been running great.

Did the tb coolant bypass on my car, with my cold air induction the tb was noticably cooler and I did notice it kept that crispness with the throttle response when the car ran at normal operating temprature, where it would lose it when it wasn't bypassed....

-Ant

Gotta tell ya guys, this is great ****. Discussion about the GREAT Third Gen cars is what it is all about. In all honesty I have tried almost every mod for my bikes and
my Camaro that exists, but nothing has worked quite the way I expected. I am an electrical engineer who goes back to the days of 67 Chevelles(396 Powerglides-*** i am an old ----). Froze my *** off the last couple of days but the ROCK is running great. I am hoping to keep the ROCK 'till my two daughters get through college. Had a collector approach me about buying my Camaro, told him I was not ready to sell. To all you young guys and fellow lovers of a fine machine you will be discussing the THIRD GEN cars 'till the day I die. If ANYONE can find a better looking automobile than a third gen, just SHOOT me. Love the site and THANKS for the feedback. THE OLD FART(50 next Dec.24) Danno

There are three reasons I did it.
1) performance gains: everyone advertises 6-8rwhp from this mod. I can't claim anything, however.
2) looks: I ground the nipples off and the throttle body looks much nicer/cleaner
3) convenience: I don't need to remove two hoses to remove my throttle body.

I just did the TB bypass on my car literally 7 minutes ago. Here's a tip that might help others. I would have taken a photo, but my gf stole the digicam.

I went to AutoZone to get a 5/8" heater hose, and I told the guy I needed a 90* angle. So he took me behind the counter and I looked through all the hoses. All these hoses are made in Mexico with no manufacturer, but the # of the hose I used is 4330. If you cut 2.5" off the long end, it will have the perfect bends to connect to the plastic valve and the inlet with 0 force on either. The only contact with anything in the area is a little bit of rub against the air intake hose. It snakes around all the sensor pigtails and the evap canister line, and looks stock.

I'm going to do the TB bypass on my 91 Z28 as well.....I just bought a BBK/Edelbrock 52MM TB....mostly everyone on here agrees that it's cheap, quick, easy mod....so.....why not do it...y aknow? I have to take all of that stuff off anyways to install my new one

The formula you refer to is bernoullis equation, is actually PV=NrT. It cannot be used in this case however because it assumes a closed system and an ideal gas. In Boston, where i live, it was the coldest day of the year last saturday, 3° not counting wind chill(wind chill was -15°). The car started and idled fine after sitting for a week. I feel the mod is more for convience and less places to leak. Even if the TB is 40° cooler, the shear mass of air flowing through it at WOT doesnt have time to heat up any appreciable amount. Lets take teh stock throttle body at WOT and flowing say 600CFM of air. Area= 48mm*2 butterfly valves=pi*r^2=.0389 ft^2 , (600ft^3/min)/.0389ft^2=15400ft/minute, divide that by 60 sec/min and you have a velocity of 256.6 ft/sec or 175.7 miles per hour. if the throttle body is 4 inches long the air is in the TB for .00116 seconds! not nearly long enough to make a large difference in the temp of the incoming air. If you can't follow my math(it's hard to show without the greek letters LOL) or find a huge error, let me know. -Mike

This mod is primarily done for throttle response, I.E. non-WOT operation. Now I'm lazy, but if you'd like to measure the CFM flow of a throttle body at, say, a 1750 rpm cruising speed... I wouldn't mind seeing the calculations.

BTW... this is a really old post.

The reason you would get ice with a carb is the fuel and air is injected into the carb which may cause icing on the buttery fly valve. Thats where carb heat would come from. With fuel injection the air and fuel are in the cylinder when mixed. This will not cause icing on the throttle body, since its all air coming in. But in the winter it may ice with high humidity and cool air. My two cents

I am going to take a wild guess that you didn't realize this post is over 5 years old...right? LOL

As long as it is been bumped...anyone have more recent experience/problems in winter with this?

Its an oldie but a goodie!

Danno, while what you're saying is probably true. How many people have had their throttle blades actually ice up because of this mod? Do we need to start a poll? I think it will be heavily lopsided in the "never happened" catagory. While I havent performed this mod on my L98, I had done it on my LS1 that I owned for 3 years(in Missouri, where winter truely sucks) and left it that way year round and never had a single issue. I bet if we were to take that poll, most if not all, will say the same thing.

If your driving around at 40 degrees or more you will never have a problem. Below that it may happen, but unlikely

Get out your Refrigeration books. It has to do with humidity, temp, and vacuum.

Air passing from a low vacuum to a high vacuum (past a restriction) will absorb heat.
The opposite of compressing air, where it will release heat. (turbos, inter coolers, sc)

Enough cooling and enough humidity and ice will form. Cold and dry no ice.

Carbs also make use of the "latent heat of vaporization" of the gasoline, changing from a liquid to a gas. When gasoline expands into a vapor it absorbs a lot of heat. Similar to adding a lot of heat to get hot water to boil. Water @ 212 F, gasoline @ 125 F or so.

Devilsown Methanol Alcohol Water Injection > General Performance > Technical Questions

Latent Heat of Vaporization


"The latent heat of vaporization of gasoline is approximately 900
Btu/gaL The vaporization of gasoline in a stoichiometric mixture
of liquid gasoline and air (without external heating) results in an air
temperature reduction of approximately 22°C(40°F)."


It is just simple physics. LOL

Since the engine bay is so warm, there is a very small chance that this could happen in the summer months, I can't say as much for the winter ones. In the summer with the tb bypass, its still warm to the touch, not cool enough to ice up though