bypassing intake manifold coolant

[dans2k]

I was doing some PCV breather plumbing on my car to stop it sucking oil into the intake. The breather goes via a metal line that also carries a line for coolant to the intake manifold. I figured to do away with this whole metal piece and bypass the coolant from the manifold with a pipe while I was about it. I can't say I noticed anything different since I did this but I know I don't need coolant running thru my intake manifold in the south east in the summer.

 

Do I need to take points for this? I don't see why but I wanted to check - I couldn't see anything in the rules

[ff2skip]

From experience, you're better off e-mailing your point questions directly to Greg.

[kbrew8991]

sounds like an emissions thing to me...?

 

I would hear Mustang people whine about this sometimes - but on those cars the coolant running through the throttle body was to cool down the EGR system. Exhaust gas is a much higher temp than coolant is, so you actually saw worse performance unless you also disabled the EGR.

 

the lesson here is to understand why coolant is being routed there before yanking it out

[hired wrench]

usually...... it's to keep the throttle from icing up in cold weather.

[TurboShortBus]

I would hear Mustang people whine about this sometimes - but on those cars the coolant running through the throttle body was to cool down the EGR system. Exhaust gas is a much higher temp than coolant is, so you actually saw worse performance unless you also disabled the EGR.

In that particular example, the EGR system doesn't do anything at WOT, so ditching it for race conditions won't do much for performance. I love the Mustang guys who bypass just the coolant lines but leave the EGR in place.

 

usually...... it's to keep the throttle from icing up in cold weather.

On an old 5.0L Mustang, I'm not sure how that's possible, since everything will be equally cold in the mornings. The EGR (injected downstream of the throttle body) is hotter than the coolant will be, anyway. From what I can tell from my experience with 5.0Ls, it's there to insulate the throttle position sensor from the adjacent, relatively hot EGR valve (this doesn't explain the 1993 Cobra intakes, but there are no such coolant lines on subsequent Fords with more distance between the TPS and EGR). YMMV on an S2000.

 

Mark

[Shawn M.]

I've been lurking around this topic for a little while, so here goes:

 

This is why it is a bad idea to bypass your throttle body coolant line:

 

First, we need to make some assumptions. The first set of these assumptions deals with the operating condition of the engine. Let’s assume that we are running the engine at full throttle at 4,000 RPM. We have a 3.0L engine that is efficient and has about an 85% volumetric efficiency. Our effective engine volume is 0.85*3.0L or 2.55L. Since we have a four stroke motor, we are pulling in 2.55L of air 2000 times a minute. Therefore we are ingesting 3.00 cubic feet of air per second, after unit conversions. Our throttle body’s inside diameter is 2.5 inches (D) and its total length is 2 inches (L).

 

The second set of assumptions deals with the air and coolant flowing through our throttle body. Let’s assume that we are pulling in air from outside the engine bay on a warm day. Our intake air is 80 degrees, Fahrenheit. At 80F and 1 atmosphere, air has the following properties:

 

Density (p): 0.0735 lbm/ft^3

Thermal conductivity (k): 0.01516 BTU/hr*ft*F

Kinematic Viscosity (v): 16.88*(10^-5) ft^2/s

Specific heat (Cp): 0.24 BTU/lbm*F

Prandtl Number (Pr): 0.708 Unitless

 

Let us also assume that our coolant is 280F and that our throttle body is not cooled significantly by the incoming air. That is, the surface temperature of the inside of the throttle body is always 280F.

 

Now we will figure out how much and how fast the air is entering the engine. Through simple calculations, knowing the throttle body dimensions and volumetric flow rate and the density of the air, we can find out the mass flow rate and velocity of the air entering the engine. These values are found to be 794 lbm/hr (m) and 88 ft/s (V).

 

We now need to know if the flow of the air is turbulent or laminar. This will allow us to determine what appropriate equations to use later. First, we need to find the Reynolds Number (a unitless number that allows one to know if the flow is turbulent or not). This is found by the equation:

 

Re = V*D/v

 

We find our Reynolds Number to be 110,000. This is definitely turbulent flow! (Anything over 10,000 is defined as fully turbulent flow)

 

We need to find our entry length, or the length of tubing needed for the flow to become fully turbulent. This value is defined as Lh = 10*D. This value is found to be 2.08 ft. This is acceptable, since there is, most likely, two feet of piping between the throttle body and the air filter.

 

Since our entry length is less than our actual piping length, we can use Dittus-Boulter equation to determine the Nusselt Number (Nu):. (Sorry about all of this name dropping)

 

Nu = 0.023*Re^.8*Pr^.4 = h*D/k

 

We find our Nusselt Number to be 214. The ‘h’ value above is the average heat transfer coefficient. Now, we can actually find the temperature of the air coming out of our throttle body. Solving for h in the above equation yields h equal to 15.58 BTU/hr*ft^2*F.

 

By using Newton’s law of cooling, where the rate of heat transfer (Q) is determined to be:

 

Q=h*(area of heat transfer)*(Surface temperature-Medium Temperature)

 

By using differential equations, natural logs and some other hocus pocus, we get the following equation:

 

Texit=Tsurface-(Tsurface-Tinlet)*exp(-h*A/m*Cp)

 

Finally, by using the above equation, the outlet temperature can be determined to be 81.3 degrees Fahrenheit.

 

Now, using the SAE J1349 correction factor, you lose ~1% of your total power for each 10 degree increase in inlet air temperature. With this 1.3 degree increase, due to the throttle body coolant, you are losing 0.13% of your power. Or, on a 200hp car, you are losing 0.26hp. By overriding the coolant flowing through your throttle body, you are risking having your throttle body freeze open in cold weather (the whole purpose of running coolant through the throttle body in the first place). Hope this clears up any confusion.

[jimbow]

Huh???????

 

On my 92 the coolant through the throttle body is strictly for preventing icing at some unholy low temperature with some level of humidity.

 

I'll check with my regional director to see if there should be any points for bypassing it. It doesn't add HP, it doesn't suptract weight. I bet it doesn't cost points if you bypass it with a connector that has the same inlet and oulet dia. as the throttle body.

[speedengineer]

Somebody has an engineering background! Thanks for doing the analysis.

 

Although, I will say that it would be pretty rare that anyone is driving their race car in sub-freezing weather. Now, if it is your street car also...then it is quite understandable.

[Shawn M.]

Somebody has an engineering background! Thanks for doing the analysis.

 

Although, I will say that it would be pretty rare that anyone is driving their race car in sub-freezing weather. Now, if it is your street car also...then it is quite understandable.

 

 

I totally stole it from the Mazda6 forums.

[kbrew8991]

if someone wants to modify their car to be slower I say let 'em do it points free

[hired wrench]

When it's cold out and humid, the water in the air is going to condense on something. If it condenses and then is exposed to freezing air, say enough air to pull the temp of the TB to freezing (ignoring that over night everything will be near the same temp because of thermal equilibrium), it'll ice. Opening the throttle usually isn;t the problem, closing it is (just ask Toyota). Once you open the throttle and are moving more air mass, it'll have a greater cooling effect, maybe enough to freeze up. Coolant lines on a TB or TB mounting flange are to keep the temps up enough to keep the TB/condensation from freezing in cold weather and high throttle situations where there is enough air mass moving to freeze things up.

 

OR in the case of an EGR to keep temps down. Because you can't regulate the temp of the air or of EGR gasses, but you can coolant, and typically water has a high specific heat, and aluminum transfers heat so well, it's easy to regulate/stabilize the temp of something else with coolant.

 

The benefits, in terms of power, would be minimal at best.

 

The only thing TB coolant lines are really good for are to use for the coolant lines for a water cooled turbo.

[jimbow]

I showed my bypass to the regional director and he opined it was a 0 point mod.

 

No HP gain, no weight reduction, got a leaking TB out of the coolant loop.

[phoenixR34]

In my region (Arizona), if you had a bypassed coolant line you would take points either modified intake manifold, modified throttle body, or both depending on where the coolant line(s) route through.

 

While you may not feel anything, not having 220deg coolant running through your throttle body could easily be contested as a performance advantage. If it's not stock as-delivered, it's modified. If it could be argued to give a performance enhancement (which cooler intake air most certainly could), it takes points somewhere.

 

There are ways to do the PCV fix on the S2000 without changing the coolant lines. I did it to my S2000.

[Greg G.]

In my region (Arizona), if you had a bypassed coolant line you would take points either modified intake manifold, modified throttle body, or both depending on where the coolant line(s) route through.

 

While you may not feel anything, not having 220deg coolant running through your throttle body could easily be contested as a performance advantage. If it's not stock as-delivered, it's modified. If it could be argued to give a performance enhancement (which cooler intake air most certainly could), it takes points somewhere.

 

There are ways to do the PCV fix on the S2000 without changing the coolant lines. I did it to my S2000.

 

I agree. Bypassing the intake manifold would require taking points for intake manifold modification. This mod is to help improve performance in warmer weather. Mods that are for performance gains that are not listed in the Rules under the No-Points Mod list either take points or are not legal.

[dans2k]

In my region (Arizona), if you had a bypassed coolant line you would take points either modified intake manifold, modified throttle body, or both depending on where the coolant line(s) route through.

 

While you may not feel anything, not having 220deg coolant running through your throttle body could easily be contested as a performance advantage. If it's not stock as-delivered, it's modified. If it could be argued to give a performance enhancement (which cooler intake air most certainly could), it takes points somewhere.

 

There are ways to do the PCV fix on the S2000 without changing the coolant lines. I did it to my S2000.

 

I agree. Bypassing the intake manifold would require taking points for intake manifold modification. This mod is to help improve performance in warmer weather. Mods that are for performance gains that are not listed in the Rules under the No-Points Mod list either take points or are not legal.

 

I think this is BS you're allowed to do other cooling modifications.

 

You're also allowed to take other systems that are on the car for road use out or modify them... IE PCV, air pump etc

 

its realy real hot at the track here in Summer its not increasing performance it may help not degrade performance due to massive heatsoak..

[sperkins]

This mod is to help improve performance in warmer weather.

 

Not true. Smart folks do that primarily to eliminate a potential coolant leak source.

I'd like to see just one mention on any of the hundreds of automotive forums, magazine articles or tech sites that suggests a performance gain in warmer weather by this so called mod.

[Varkwso]

This mod is to help improve performance in warmer weather.

,,,

Not true. Smart folks do that primarily to eliminate a potential coolant leak source.

I'd like to see just one mention on any of the hundreds of automotive forums, magazine articles or tech sites that suggests a performance gain in warmer weather by this so called mod.

 

 

It is not a gain....come here in August and do side by side comparisons...may be a point mod ....but it is not a gain...

[TurboShortBus]

From what I understand, whether or not a modification makes a difference on your car does not necessarily justify the associated points. Rather, the modification making a difference on a car, somewhere out there, is what justifies the points. This modification on an S2000 might not make a bit more power, but there might be another car out there (that people further up the ladder than me know about) that triples its RWHP with the same modification, and that car is the one that the rule is based on. Each individual rule likely cannot be written to pick and choose which car(s) it specifically applies to. There are plenty of rules and points that would apply to seemingly minor modifications on my car (don't get me started on double-whammy points for tubular K-members), but I have learned to throw my hands up and walk away.

 

Here is a solution:

1. Rip off the EGR coolant lines and anything else you don't like.

2. Reclass the car based on dyno results and weight.

3. Drive in anger.

 

Of course, none of the above is official; it is just my understanding of how/why things are done.

 

Mark

[kbrew8991]

but I have learned to throw my hands up and walk away

Mark

You ARE becoming wise

[Cobra4B]

I'm putting my TTA build Z06 back together and just installed the intake manifold and TB last night. I was debating bypssing the TB coolant connections. Guess I'll just hook them up and forget about it.

[Varkwso]

but I have learned to throw my hands up and walk away

Mark

You ARE becoming wise

 

I am just glad I do not make the rules - I only enforce them as I understand them...

 

We are all getting wiser...

[dans2k]

I think if anyone did gain horsepower from it then it shows how much of a bad thing coolant in the TB is!

 

I guess it realy doesn't matter I'm not running TT till october I can connect it up again

[Varkwso]

To be fair - some mods do make no difference on some cars and some make a ton. I think this is one of them.

 

The lightweight flywheel and clutch are a huge free mod advantage to the mod motors and LS motors. May be good for others but I do not know.

[drivinhardz06]

To be fair - some mods do make no difference on some cars and some make a ton. I think this is one of them.

 

The lightweight flywheel and clutch are a huge free mod advantage to the mod motors and LS motors. May be good for others but I do not know.

 

great mod for any big motor that uses a big dia, heavy FW and plate. small engines with already small/light clutches probably don't get the same advantage

[dans2k]

To be fair - some mods do make no difference on some cars and some make a ton. I think this is one of them.

 

what car does it make a difference on?