Help needed ASAP

[Captain Obvious]

if I remove all the lost time stuck in the pits due to vapor lock alone, we'd gain over 100 laps. That would have moved us up from 30th place to around 13th place. Fix the other fuel delivery issues to make the car run better and we could have been a top 10 car without actually being much faster than we are now.

Absolutely. That's beyond "respectable" and into "enviable".

I looked at the float geometry last night to refresh my memory, and I'm not seeing an obvious explanation for mixture changes under lateral G's. At least nothing that wasn't symmetric side to side. Because of the direction of the float hinge pin and the position of the hinge on the float itself, I could maybe see something under hard acceleration or deceleration, but side to side isn't obvious. Not saying there isn't a relationship, just saying that it doesn't jump out at someone not trained in the art like myself.

I'd love to hear what the experts like Steve and Bruce at ZT say when you talk it over with them.

I thought of something I should have suggested a long time ago... When you are having the stuttering problem, have you reached for a handful of enrichment cable? That could tell you if you are rich or lean while the problem is occurring. If the problem clears up when you pull the choke and lower the nozzles, it's pretty clear that you are starving for fuel. Vice-versa for making the problem worse if you're already drowning.

Out of curiosity, what was your average gas mileage? You said your drivers were getting roughly 1.5 hours out of ten gallons of fuel. About how many miles is that?

[Jeff G 78]

I should have been clearer when I said the problem was after right hand corners. Nelson Ledges is a VERY fast track and it flows very well turn-to-turn. The one RH turn is very tight and leads onto the front straight and the other is a 180° banked turn leading to the back straight. I'm not sure that the direction of the turns was a factor as much as the loading followed by a hard acceleration run.

I did not try to open the enrichment (choke) THIS race, so I can't say if it would have helped. I have tried it in the past when the car wouldn't rev past 5k RPM and it did not help.

I haven't gotten the fuel logs yet from my teammate, but when I do, I'll calculate the GPH (gallons per hour) and MPG. GPH is the standard race terminology since that's what matters to us. I'd say we are about 7 GPH which is in the ballpark for our car.

[Bonzi Lon]

Just throwing something out there. You said you are using the stock fuel rail, it should be the same as my 73. Can you modify it? For example, the front 2 mounts have steel pads, can they be removed and replaced with heat resistant material, ie carb & fuel pump? Use the same material between the head and bracket on the carb side. The bolt itself would have some transfer. Heat resistant bolts? Do all 4 mounting points need to be attached? Using the original silver heat resistant wrap? Just a few ideas.

Bonzi Lon

[Jeff G 78]

Hey Bonzi, yes, the plan is to do exactly what you said. The plan is to remove the steel pads from the front rail mounts and replace them with some sort of insulators like the carb/fuel pump spacers. If I drill out the holes in the rail mounts and run the insulators on both sides of the rail brackets, I think the heat transfer through the bolts should be greatly reduced. There is no need to run all four mounts either. 2 or 3 should be plenty. I am still running the OE silver asbestos(?) wrap. I will replace it with a more modern heat wrap to improve the insulating properties.

I am thinking about engineering a simple loop cooler and pump system that would run a water pipe along side the fuel pipes in the rail and under the heat wrap. I would make a loop in the airstream, install a small reservoir and use a tiny electric pump on a toggle switch. It could be switched on only at high ambient temps or during pit stops to keep the rail cool.

Anybody ever tried this?

[madkaw]

Google DIY tune for your wideband. I think you need to concentrate on tune before assuming something else is wrong. Ask me how I know this:) I dynoed my Z at Zcon and it showed rich and a power drop at 5300, but for the most part my plugs looked good-I didn't have a wideband at that time so I was left guessing. It turned out that I didn't have my carbs synced properly at 3000rpm and I was pulling off of mostly one carb-great for MPG-lousy for power. My floats were set up to stock specs, but i had to tweak them beyond that point for best AFR and power. I'm not sure i buy into the spill-over theroy. Any fuel in the filter? You said it ran worse when the fuel tank was low-did this tie into when it bogged on right handers? If your fuel rail is set-up in the stock position, I'm not sure I buy into vapor lock either. Pulling the chokes to enrichen fuel that might not be there(floats) will only help diagnose one aspect of a fuel problem.

I know you have looked at the tank, but look again, especially your sending unit return line. I had what looked like a brand new unit and it had a bug or something in it that partially blocked the return line and played havoc with me. It happened intermittmently to make it harder to diagnose.

The 150$ or so spent on the wideband will be well worth the investment.

[Bonzi Lon]

As a teenager I used to pit crew for a drag racer. One of the tricks was a box around the fuel pump, filled with ice right before the race. Later outlawed.

The original silver wrap got me to thinking about a newer type of material, like No-Mex (sp), that is used in fire suits. And a heat resistant gel used in the movies.

Watching "Modern Marvels, Spirits", it said 'alcohol vaporizes at about 170 degrees F'. Is there any alcohol used in your fuel?

An inexpensive hand held laser thermometer might be a useful 'cool tool'.

Bonzi Lon

[Jeff G 78]

Bonzi Lon, all gas in this region has 10% ethanol, so yes, it will vaporize at a lower temp than pure gasoline. I do have a no-touch pyrometer, but we never checked to see just how hot the rail was getting. The tools were at the other end of the paddock and I forgot I had even brought it to the race. I think that with the right testing and countermeasures, I can eliminate all of the fuel heat issues. At that point, we can concentrate on the actual tuning.

[Captain Obvious]

The plan is to remove the steel pads from the front rail mounts and replace them with some sort of insulators like the carb/fuel pump spacers.

I'm not a thermo expert but I'm skeptical about the amount of heat that is conducted up through those mounts. I guess any little bit helps though, right? In any event, After you drill the mount hole larger, I'd be happy to make some plastic insulating inserts for you once you get to that point.

Now that you aren't using the mechanical fuel pump at all, how about completely re-routing the fuel lines across the firewall and onto the driver's side fender instead. Don't ever mount it to the block at all. I'm sure I've seen pics here on the forum somewhere of that mod.

[Jeff G 78]

The ONLY reason to keep the OE rail is because of the return system. The rail has a nice loop that would have to be replicated. We have run it both with and without the return and so far, it doesn't seem to really care one way or the other. I agree that with no return, we could reroute the supply hose and keep it completely away from the engine.

As for the heat transfer through the mounts, I wouldn't have thought so either until I saw the exhaust manifold glowing red. That means the head is pretty damn hot as well so some of that heat will certainly transfer to the rail. Every little bit contributes.

I will go through the McMaster Carr catalog and see what kind of insulators I can find. I'm thinking ceramic or fiber-plastic like the mechanical fuel pump uses.

[Captain Obvious]

Yeah, that's a good point about the exhaust manifold. It's hot.

As for what to make the insulators out of... I was thinking Delrin (acetal) because it machines like a dream. Well, that and I have it on hand. Haven't checked the thermal conductivity and it's probably not as good as ceramic, but it's gotta be a whole lot better than steel!

[Jeff G 78]

Yeah, that's a good point about the exhaust manifold. It's hot.

As for what to make the insulators out of... I was thinking Delrin (acetal) because it machines like a dream. Well, that and I have it on hand. Haven't checked the thermal conductivity and it's probably not as good as ceramic, but it's gotta be a whole lot better than steel!

http://plastics.dupont.com/plastics/pdflit/americas/delrin/230323c.pdf I'm no materials expert, but it looks like it might work. The only obstacle might be the melting point of Delrin.

[black gold man]

You can see the car here.

50 sec in z being passed and passed again at 6 .15

Fiero Crash

Looks like fun

Edited October 15, 2011 by black gold man