Before intake temps ran avg. of 155..lowest 120...highest 189
Now avg of 125...lowest 112...highest....140

Avgs are taken from normal summer driving...different datamaster files I've logged were used.

 

interesting, so it is more than a "hype" mod.

 

Thanks for the numbers! It never was a "hype" mod... it's just not a mod to bring you more then -maybe- 1 or 2 horsepower.

And it's certainly not a track-only mod.

People expect a miracle from doing it; they don't see the miracle, and then accuse it of being worthless.

 

Thats cool. Good results.

What kind of intake to you have?? The dual snorkle, home made, etc??


189, *gasp* almost as hot as the engine itself.

Outside air temps about the same?

 

Those are heatsoaked numbers, right? They don't really tell what the actual air temperature is. It more likely tells what the temperature of the plenum's aluminum is.

 

It's the temp that the sensor for incoming air is reading.

I have the dual snorkel intake, but I think I'm going to scrap it. It seems pretty restrictive to me.

 

BTW, these ae 80-90 degree days, and my car does sit low, so the air is coming off the hot road essentially

 

What I'm getting at is that the sensor is affected by it's surrounding heat. It's sitting in the plenum (you have the LB9, right?), and is getting soaked with the heat of the plenum. So, it's temperature isn't exactly the incoming air temperature. It's the biased air temperature. The sensor is metal, and is sitting in the metal plenum, and is subject to heat transfer, thereby altering it's temperature readings. The sensor doesn't measure corrected temperatures.

Since the TB bypass removes the coolant flow through the TB and decreasing the temperature on the plenum, which in turn decreases the temperature on the sensor, it's readings naturally drop. That doesn't necessarily equate to an 8-49 degree drop in the air flowing over the sensor. There probably is some miniscule effect, but it is not a 1:1 correlation in absolute temperatures. Someone reading the data may get the wrong impression. I just don't want someone to walk away thinking the TB bypass will reduce the air temperature by 30 degrees, because it won't.

The effect on air flowing through the TB and plenum can be modeled once the velocity is known. The faster the air, the less it can pick up from conduction of a static source, the TB, plenum, and runners, in this case. Which means the higher the revs, the faster the air flow, the less it is effected. Even at idle the air is moving fairly quick. This is essentially the same reason why having no thermostat will cause an engine to run hotter than with a thermostat, because time is needed for conduction to take place. Or another example, pass your finger through a flame quickly and you don't really feel it. Pass it through slowly, and it hurts. Leave it there, and it'll burn a nice mark into your skin.

I'm sure NASA has some published equations that can be used or adapted to model this system...or even a rudimentary equation from a thermodynamics book. I'm just too lazy to go look for it. I'd figure at the very least you'd need to know the air velocity and the heat transfer coefficient of aluminum.

 

I would disagree with the "1-2 hp" increase. There is definetly more there to gain. After I did the mod I gained 5-10 easy, though I have no proof. I have noticed a very significant change when the intake manifold is heat soaked. One real easy way to tell is when doing standing burnouts. Without the mod I couldn't (when warm). After, no problem. It does become more difficult after it sits idle for a while. For this reason, I will be shaving down my intake manifold when I replace my cam to decrease the thermal mass present. This will let the manifold keep a lower temperature due to the incoming air and resist heating from the engine.

BTW Don't replace the dual snorkle setup. I did a test to measure the pressure just upstream of the throttle body. I measured .072psi (2inH2)of vaccuum max at full throttle, 5000RPM. After I did this experiment, I am hesitant to buy any K&N filters, performance MAF, or do the MAF-MAP conversion.

 

You're not understanding my point.

Of course the aluminum is going to affect the temperature the sensor that's located in the plenum is reading. That's WHY people do this "mod." I did it because I had the TB off already and figured what the hell.

The sensor reads the temp that the air going into the combustion chambers is. The cooler the temp going in, the more power you will be putting down because cold air is more dense than hot air. That's why you car feels more powerful in the winter and why cooler nights at the track yield better times.

Notice in my posts I never did say that I gained any HP. I'm not going to make a statement that bold. Only thing I posted was that there WAS a measurable difference in the air coming in.

If you'd measure the air coming into my system at the air filters, yes it'd be lower, but there's no sense in measuring that since the air coming into the filters is heated up before it gets to the combustion chambers. The purpose of the TB Coolant was to warm the TB up and keep it from freezing in cold weather. I've seen snow in only 3 years living down here....it hardly ever gets that cold. By doing the buypass, I'm simply removing one more thing that heats up incoming air.


BTW, not an L98 It's an LB9.

 

TB bypass is a worthy mod. The next one would be some plenium spacers so the engine stop transfering heat into it. Id love to be able to touch my upper plenium and feel no heat which would still be 97-98f.

Matt

 

get some sheet metal, some cutters, gloves, and a drill. I've seen a car (carbed) w/the entire engine covered except for the carb sticking out. Mirror finish too. Kind of overkill, but you could also work into it a distributor heat shield to keep Karl on the road too

 

If your intake airtemp IS that much lower- Then heck- I'll say it for you- YOU ARE GAINING HP. You are definately correct about having a cooler more dense fuel charge.

A side note: I am strongly debating ceramic coating the superram plenium I am fabricating to lower intake heat.

 

Actually, I am understanding your point, but you're not understanding mine.

I'm saying the temperature you are reading is biased by the aluminum temperature. The sensor in the plenum is known to not read the actual air temperature coming in. It's not reading the actual air temperature going into the combustion chamber. The temperature being read is biased.

I'm also saying that just because the temperature you read drops by 30*F doesn't mean that the true air temp drops by 30*F.

I did the mod also, for the same reason you did. I had the TB off.

 

HEy,

I've read a couple of times about the intake spacer, but I am unsure what bennefit that will give you. Won't the heat just be transferred from the manifold into the plenum through the spacer? What would you make the spacer out of? My intake is very hot and I have done the TB mod but it's still hot! I can make a spacer, I have access to a machine shop, but I am unsure how it would help or what to make it out of.

Dale

 

Why would any air temp sensor be in the intake??? Our little V6s have it in the plastic intake tubing???


Plywood conducts the least ammount of heat. It is an old racers trick but they wore out quick from being soaked with gas. We would not have the problem.

Id visit a local plastic company that sells sheets, and ask them what can take the heat 250-300f but does not transfer heat. The old GM 4bb gaskets were plastic but not sure what kind.

Matt

 

That's why the correct 3rd gen term for the sensor is "MAT" - Manifold Air Temp sensor. On v8's, it's in the aluminum manifold.

IAT (Inlet Air Temp) is the 4th gen term, when GM moved it over to the airbox.

Now ya know why I'm always **** about "It's MAT! Not IAT!"

 

No ****. That's what I'm trying to get across. I know that the temperature is biased by the aluminum temperatue, but if you reduce the aluminum temperature (which is why the mod is done...it reduces the TB temp) then you'll in turn reduce the air flowing over the aluminum's tempeature.

 

As I said, you are not understanding what I am saying. I am doubting that the temperature drops at all. I'd doubt if there's even a 1*F shift in air temperature. I had tried to explain that by telling you that for a heat source to heat very fast moving non-diffused air, the heat source would need to be very high in temperature. The plenum and TB simply is not hot enough to heat air like a hair dryer.

 

Check out my all new TV reality show.

PISSING CONTEST

Only rule is I get to pee on you first.

 

K, tell that to all the guys icing down their plenums at the track.


Guess we could all run 220 stats since it really doesn't matter how hot the engine block is either. It wont' affect the power output.

 

Pissing contest? Wow. Did you know that the earth is not flat? Ignorance is bliss, right? It's not a pissing contest, it's an explanation of thoughts. There's no need for name calling or infantile behavior. I'm sorry you are getting flustered by theories, maybe you can disprove our current understanding of thermodynamics. Please talk to NASA if you do.

Sure, I'll tell those people icing down their intake. But, by your definition, it would be better to not have a thermostat than to have one. A thermostat stops flow. Air doesn't stop in the intake. So, your analogy is not the inverse model.

Since you brought up racers, and power, and basically WOT. A 48mm TB flows about 600cfm, right?

48mm TB has 2 butterflies. Radius of each butterfly = 24mm = 24mm/25.4 mm/inch = 0.945inch=.0787ft

2*Area of each butterfly= 2*pi*0.0787*0.0787 = .0389 ft^2

600cfm/.0389ft^2= 15402.04ft/minute=256.7ft/sec= approx 174.6mph

I'll let you calculate the time the air is in the intake at 174.6mph and I'll let you calculate how much the air temperature changes when it goes through a negligble length at 174.6 mph.

Anyway, this is an old argument. All I wanted to say was that the air temperature is not a true 30*F drop, as was implied by the first post.

 

What's probably most important is, assuming I read the first post correctly, that the computer sees the 30 degree drop.

 

I hate to get in the middle of this argument but what I'm gonna do is give you a good estimate of what the difference in heat transfer to the air is. But you'll have to wait a couple of days. Don't forget that you have conduction as well as radiation going on inside the TB. I'll assume the air speed that 91Z28-350 gave, and an initial air temp of ambient at about 90°. I won't take a guess at the air temp drop because I don't want to fuel the fire.

On a side note, does the TB bypass just involve capping off the coolant to the TB? Because I was thinking (assuming that the TB bypass is worth it) if you're worried about the TB being too cold in the winter, couldn't you just rig up a thermostat so that it closes when the TB gets too hot?

 

You can express your thoughts as much as you want. It's just going to go back and forth, much for the same reason the arrguments go back and forth over the no thermostat example you propose as well. You have racers that claim it'll run too hot, and ones that claim it'll run too cold.

https://www.thirdgen.org/techbb2/sho...ack+thermostat

That's one a while back ago....there used to be like a 4-5 page thread.

 

https://www.thirdgen.org/techbb2/sho...ove+thermostat

another

 

I hate to butt in to this lovely conversation, but I did notice that after I did the mod, the engine did run better at idle and up. At idle, since the air moves slower, it can pick up the heat better, causing less power.

One can think that there is an insulating air pocket against the wall of the intake so it shouldn't matter what temp the intake is. Ideally there is no such layer (polished intake) so it will cause a slight increase in air temp.

Regardless, anything you can do to help reduce air flow or temp will help. Obviously, Chevy was trying to heat the air for cold temp situations. If they can heat it, we can cool it by the same means.


Proof is in the pudding, the mod helps for whatever reason!

 

Yeah, it is going a bit back and forth.

camaro_junkie - it isn't blocking off the TB, it's bypassing the TB. So, you see the coolant hose from the intake to the TB and the TB to the heater valve, just take the TB out of that and connect a hose from the manifold to the heater valve. I think you can put in a valve of some kind to reroute the coolant based on temp, though I'm not familiar with all the little gadgets out there. I know you could manually do it through some plumbing attachments, but that's not quite what you wanted.

There's one thing that this mod does do is make you run a tad richer because of the temperature variation with the MAT. It's similar to the shift you see when you relocate the MAT. You may need to tweak your prom a bit, depending on your set up. You can monitor your BLMs when the car is in closed loop and you'll see what I mean.

How are you going to measure these, or are you using the thermodynamics equations? There's actually conduction, radiation and convection going on, since the air going through has not been split up like through a radiator grille. What get's picked up by conduction is stirred by the eddies. But, that's harder to model. The easiest is probably measurement, but that's work.

I'm eager to see your results!

 

Ah, memories...

 

91Z28-350:
I don't think that there's any convection because the air is flowing through the TB too fast, (convection would happen if some particular air particles were swirling around inside the TB for a length of time, but that just won't happen) but even if that weren't the case, you could neglect it since it will be really small compared to that of radiation and conduction. It's not really a lot of work to use equations to figure out the change in air temp due to the bypass. You can do it with a couple of simple equations. It will have a large error factor, but at least then you'll know if its 0.1°, 1° or 10°.

Also, thanks for TB bypass explanation. I've heard of it, but not about it. That's not something I will spend time on any time soon, but maybe in the future...

 

It was 81 degrees tonight. IA temp read 89.4 all night long pretty much.


After driving 120 miles, getting into a few unsanctioned automotive confrontations (street races) and pulling into a parking lot (right after one said race), I popped my hood, and felt my plenum and my TB. They both felt like the car hadn't been ran all day. This was when my temp gauge was reading 220 too.

 

OK Tom...what about mine. I have the Dual Snorkal Intake...is mine an IAT??? The Sensor is drilled right into the air box??? Or is MAT a V8 only term???

 

I was wondering about this also. Mine is also on the air box on my 89 RS. Hm I'm wondering if GM made a change around 88 or 89 on this set up of the 2.8. *shrug*

-Dan

 

The temp sensor for all of us V6's is an IAT and it is in the plastic before the MAF.

MAT is a V8 thing till after 92 I assume.

Matt