Heatsoaking Fuel Rail - Fix?

[TURBO2GO]

Regan thanks for creating yet another worry for my brain... LOL

 

[Mac Attack]

191F? That is hot. That's almost vaporlock territory as you pointed out. If mine were running I would get a reading on mine. Hopefully someone else can get you readings on theirs.

For future reference, what were some of the other conditions (i.e. fuel tank level, adjacent supercharger, head, and intake manifold surface temps)?

So you've noticed this with both the old Walbro and the new Denso pump then? I thought it could have been from the failing Walbro because of the early June date when you posted the concern.

 

[RYU]

191F? That is hot. That's almost vaporlock territory as you pointed out. If mine were running I would get a reading on mine. Hopefully someone else can get you readings on theirs.

For future reference, what were some of the other conditions (i.e. fuel tank level, adjacent supercharger, head, and intake manifold surface temps)?

So you've noticed this with both the old Walbro and the new Denso pump then? I thought it could have been from the failing Walbro because of the early June date when you posted the concern.

I drove the NSX again today. I'll document the different temps from the different components. I'm at about 3/4 full. Still lots of fuel in there.

I never did take any temp measurements with the Walbro or the OEM pump for that matter. I wasn't really concerned and I also had the CF fuel rail covers on there also. I would really be quite surprised if it's the Denso pump though. I think the NSX fuel rails get hot normally, or it's the CTSC fuel rails that get hot or perhaps it's the injector swap itself that's causing it get hot.

I wish some folks could chime and let us know if their setups run hot too. Just touch it.. you'll know.

 

[BATMANs]

i was under the impression that part of a warmed up engine is that the fuel is warmed up so that it helps better atomize the fuel. Maybe even help vaporize the fuel for greater fuel surface area that should equate to a fuller and complete combustion.

 

[RYU]

Here's some more interesting information.

I decided to drive home with the water injection turned on. For those that don't know my setup.. I'm spraying 100% water with a small nozzle (too small) before the TB. It was the same ambient temp outside as yesterday.

The Autorotor was nearly as hot as the rails yesterday. I suspect with the water spray today it's why this is running cooler.

I will hypothesize my rails are heating up due to convection. They're cooler by a little bit today.

The IM temp was interesting. I'm not sure why this reads as hot as the fuel rails were yesterday. Adnan!!! I need those phenolic gaskets man!!! I'm about ready to have some made because you're taking forever. I kid, I kid...

This makes sense..

Just to check the calibration on the my little laser gun... it's pretty close to what the OEM ECT sensor was reading at this time. +/- 5F

just for fun.. thought i'd measure the TB also. I thought it'd be cooler actually.

 

[goldNSX]

Interesting results. You should add more infos like outside temp?, city driving?, cruising or sporty driving?

In my case with the newest version of the CTSC and cruising at 50 mph with outside temps of around 77 F (25 degr. C) I still have cool fuel rails while the Lysholm gets around handwarm. The snout always gets to around 140 F as the Tension of the belt and the bearings get hot.

 

[syndicate]

I think the fuel is not getting hot because it has too high heat capacity. It is not in the rail long enough to take on the heat from the rail. Would there be any added benefit to ceramic coating the blades in the charger or anything on or in the surrounding area?

 

[RYU]

These were the conditions on both days. It was approx 80-85F ambient temps. Roughly travelled 20 miles in horrid LA traffic. Total travel time was about 45mins-1hr. It doesn't really get hot until about 30mins into the drive. Then everything in the engine bay just heat soaks and it remains at those temps for a while.

If you dont' drive the car in that kind of heat for at least that long you probably will not be able to replicate these conditions. I was boosting mildly just thru normal traffic weaving ins/outs.

Hope you guys can posts your results. It would be very helpful. After further inspection the heat may be coming up from the injectors since I did not use the OEM phenolic o-ring washers. If this is the case the RDX guys are having the same issue but L_Rao says he's using them on his so I really don't know how it's possible to install that thick plastic o-ring in there and still have the injectors fit and not cause a fire.

 

[goldNSX]

I wonder of someone could make a downforcelike intake snorkel for the passenger side of the car.

We do this but don't know when it's finished. It should even carry a fan.

If you dont' drive the car in that kind of heat for at least that long you probably will not be able to replicate these conditions. I was boosting mildly just thru normal traffic weaving ins/outs.

I can't replicate these conditions but I'm astonished to see your engine bay getting heat-soaked. Your engine bay is simply in the lack of a cooling air flow. I even have the OEM engine cover in place which actually helps directing the air flow from the right side to the rear exhaust header. My car is mainly moving at >35 mph and my fuel rails remain cool, very cool, esp. compared to the blower unit. I'm feared of the consequences for the electronics in the engine bay with that heat.

 

[turbolence46]

Next time I drive my car I'll post my results on the whipple SC. My covers are off too.

 

[RYU]

I can't replicate these conditions but I'm astonished to see your engine bay getting heat-soaked. Your engine bay is simply in the lack of a cooling air flow. I even have the OEM engine cover in place which actually helps directing the air flow from the right side to the rear exhaust header. My car is mainly moving at >35 mph and my fuel rails remain cool, very cool, esp. compared to the blower unit. I'm feared of the consequences for the electronics in the engine bay with that heat.

What headers are you running?

I should also try this again with my engine cover in place.

 

[A.S. Motorsport]

Very very interesting information, I was thinking of the issue a week or two back and sketched a small insulator setup.
Now my main concern is how much does the fuel atomisation and volume change due to this heat when the fuel pump is at full pressure. (is there enough transfer time to effect the particles)

BATMANs, point is correct on a gas stove in which it coils surround the heat source heating the gas vaporizing it further.
below ideal temperature you'll have a yellow/orange flame once it reaches idle operating temperature it turns blue signifying full combustion.

Torches occasionally have the same effect.


Now in I recall reading once that fuel heat is a factor in a diesel engine, diesel being such a crude fuel requiring heat and pressure to combust it will react to fuel temp.
That being said don't large ship diesel two stroke engines pre-heat the fuel to make it flow? (btw that isn't regular diesel it's more crude oil)

Back to the NSX,
We all know we'd like to have our intake air temperature as low as possible so we can pack more oxygen in the engine.
Same could be said for fuel if it's colder it's denser meaning the injection nozzle is spraying more fuel practicals to mix with oxygen.

Thus a "thicker mixture" so to speak.

If the fuel heats up and it's atoms move further apart thus lowering it's effectiveness would this have adverse effect on a AFR?
Just as hot air will effect combustion.

This also reminds me of working on classic cars that have several provisions in the carburetor to control air and possible fuel temperature.
The "Icing" effect a carburetor can have is similar in principle to a AC/Fridge, when humid air is sucked in at high flow rate the venturi effect and fuel spray can cause the localized icing of the water particles.

Dyno testing the cold fuel vs hot fuel is rather tricky you'd need a external fuel pump and tank and switch between that and internal.

If we where able to test a engine at air temperature 10c and fuel temp 20c and then run a test at air 10c and fuel 40c we could compare data.

Update,
After some digging around i found the following:

Gasoline expands 1 percent for every 15 degrees Fahrenheit.

 

[RYU]

Very very interesting information, I was thinking of the issue a week or two back and sketched a small insulator setup.
Now my main concern is how much does the fuel atomisation and volume change due to this heat when the fuel pump is at full pressure. (is there enough transfer time to effect the particles)

I'd be interested in the insulator setup you had in mind. Also thought the same on the fuel pressure. It's so high that the gas is likely traveling thru the rails so fast it may not matter.

 

[A.S. Motorsport]

Did some calculations yesterday night and it looks like every 15F you drop fuel temp your gaining 0.14 AFR to get a 0.5 AFR gain you'd need 53.57F drop.

 

[goldNSX]

What headers are you running?

I should also try this again with my engine cover in place.

Sorry for the late reply. I've 97+ headers with heat shields. They let the engine bay a little bit cooler than an aftermarket header system I know. The key point to adress the problem of the hot air ballon enginebay is to get cold air from the passanger side over the engine, while moving but even more in traffic jam.

A therminal gasket between the charger unit and the engine may help to keep temps down but the main effect of heating up the SC unit is the snout and the pulley with it's bearings. They get really hot and all of the heat energy is transferred to the SC unit and it's impellers.

 

[A.S. Motorsport]

 

[RYU]

I need help thinking thru something...

Let's talk ceramic coatings.

I'm considering ceramic coating my CT headers. This has been proven to work in others cars to keep under-hood temps dramatically cooler. I then got to thinking about ceramic coating my CTSC intake manifold. If coated exhaust manifolds helps keep heat IN then will coating the intake manifold have the opposite affect I'm looking for? It will keep the heat in and result in higher IATs?

Theoretically i'm torn on whether coating the IM will result in a cooler IAT (ward off heat soak) or warmer IAT (insulated hot pressurized boost).

 

[goldNSX]

Coating headers WILL help for sure.

Coating the intake mainfold will have the opposite effect. Where should all the thermic energy go which comes from the snout and the engine?

 

[RYU]

i think it would depend on how much heat does 7psi of boost create on the 1.7L Autorotor (assuming heatsoak is not a factor). In other words if the air temp around the engine is 160F and my IAT is 130F then I could see the benefit of the ceramic coating.

Though, I think I just convinced myself the benefit is marginal. I think the best bang for buck is coating the headers and Adnan's phenolic spacers/gaskets.