Second Gear Problem

PostPost by: type26owner » Thu Dec 09, 2004 2:10 am

Since I've had a chance to get comfortable to the newly installed RE92 tires capabilities I've developed a new problem at modest speeds. Apparently these tires have enough lateral bite to cause the Webers to now fuel starve. This is getting really annoying now. Is there a cure to apply to the carbies to stop this effect? Help!
-Keith
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PostPost by: lotuselanman » Thu Dec 09, 2004 8:14 am

<_<
Gidday,
New one on me, suggest you check the float levels, max and minium.
See ya, Les
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PostPost by: type26owner » Thu Dec 09, 2004 4:10 pm

Guess it's time to call up Mike Pierce at Pierce Manifolds and have a technical chat about fuel starvation issues. I can't imagine this was never resolved but I'm a rookie and don't know squat about the different DCOE designs over the years. Hey, maybe it was not a problem since the tires at that time never allowed this starvation to happen ever on road cars.

Hi Les, didya know you can check the fuel level in the 'wells' while the engine is idling using a custom made pipette? Awhile back I've posted here lots of technical info on Weber tuning which is not in any of the books and covered that very subject.

Just about to go into another tuning/learning phase to map out the affect of two-phase flow across the main jet/air corrector matrix. Should be able to take slow motion movies of the two-phase flow happening in my transparent testing well and post a link to it so everyone can see how the carbie actually works. Will try to do this over my Xmas break.

-Keith
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PostPost by: type26owner » Thu Dec 09, 2004 8:28 pm

Talked with Gron at Pierce Manifolds and he said it's either the fuel level is too high and the fuel is splashing up into the air correctors and the mixture is getting so fat it fouls out the spark plugs or the fuel is sloshing away from the bottomside supply holes which feed the wells and it leans out the mixture either way the engine dies. He suggested trying lowering the fuel level by another 1.5mm from the stock value first. If that does not work then add tube extensions that press-fit into the well supply holes so the fuel is picked up about another 25mm lower down in the carb body. By making the tubes the right length and chamfering the bottoms then even if they come loose the removable bottom access cover will still capture them from completely falling out. He also suggested I do the same thing for the holes feeding the idle jets but his reasoning behind this escapes me at the moment. He claims to have cured this problem with the extension tubes on Formula Atlantic cars. I always thought those Toyota knockoffs had FI instead of carbies? :rolleyes:

Hey Mike Ostrov, If you're done trying out my AFM I need it back so I can measure this happening realtime and eliminate the guessing part of this diagnosis. :)
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PostPost by: rgh0 » Fri Dec 10, 2004 8:04 am

Kieth

I have seen the jet well, tube modifications to help prevent fuel coming in through the air correctors air inlet used on open wheelers with wings and sticky tyres that run Webers. The cover over the jets is raised about 25mm with a tube the diameter of the jet well and the jets modified to raise the air intake to ensure the air correctors dont flood. I presume the fuel intakes to the jets may also have been modified but I have never looked that closely.

However I have never seen it needed on any sort of sports cars, even ones with a lot more cornering grip than my Elan. I have never seen the problem on my car. I suspect there is some other problem causing your symptons that can be corrected without modifying the jet well and jets.

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PostPost by: type26owner » Fri Dec 10, 2004 4:29 pm

Hi Rohan,
Thanks for the comments. I'm well aware of this potentially being some other problem. I always start any diagnostics related to the engine cutting out by thoroughly examining the electrics first. It's at least ten times easier and faster then tackling the induction system. Planned to also have my VOM attached to the primary circuit of the coil. Suppose I could hook up my timing light too but I've got no way to pass the leads through the firewall. Hmmmm.....

This dying only happens in right-hand corners. It cuts off clean like the ignition is shut off but when the cornering forces are reduced it takes a second to sputter back so it's firing on all four again. Never expected to have this problem now. IIRC, we removed the Webers from the Lotus41 for this very reason back when we were still running Goodyear Blue Streaks tires and we had no wings. Re-engineering the Tecalemit-Jackson fuel injection and getting it to work well was the way we made the problem go away around 68 or 69.
-Keith
p.s. Do you have any experience with modifying the spray pattern of fuel injection nozzles? The system in a constant flow mechanical type. Been looking at adding deflectors since the nozzles now direct a solid stream of fuel about 3mm in diameter which only splashes off the head of the intake valve. Now that we don't blow up the BRM every other year like we used to do I'm finding that within about 100 hours of time on the engine all the cylinders need to be resleeved. Making the assumption this is not a normal wear rate for an engine which is never revved over 8200 rpms anymore. Also assuming that what's happening is the oil film is being diluted and removed off the cylinder walls because it's awash with still liquid fuel. The intake ports are not being cooled by any fuel vaporization.
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PostPost by: 1964 S1 » Sat Dec 11, 2004 4:30 am

Find out what Jim Clark's carb setup at the Nurburgring in 1962 with the 23 was! He made it through many right handers flat out...smooth as silk no doubt. Do you think you're pulling more g's than he was? I'm guessing a 23 goes around corners like a big shifter kart. Do your new tires feel all that much stickier?
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PostPost by: rgh0 » Sat Dec 11, 2004 6:21 am

Keith

I use a rule of thumb that everything in a race engine wears out 10 times faster than a road engine because of the constant full throttle max revs usage. So 100 hrs is equivalent to 1000 hrs in a road engine which is probably 30 to 40 thousand miles so the wear rate is not that bad. However with modern oils you should not be wearing out the bores that quickly. I dont see that rate of wear in my Elan race engines running on carbs with a 8300 rpm limiter. What sort of piston ring pack are you running, a modern light weight one or the original ?

Your theory is probably right about fuel washing the walls to much

Dont know much about fuel injection because I have never played much with. However you may want to look at the injection nozzles used on the early Bosch mechanical fuel injection systems to get some ideas how to modify yours or altenatively maybe those nozzles will work with your T-J system. As the Bosch system was designed for up market road cars the nozzles probably have a better spray pattern than the relatively crude T-J race system.

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PostPost by: rgh0 » Sat Dec 11, 2004 6:23 am

Keith

With the timing light

Just run the leads out of the bonnet and around the windscreen, alternatively just leave the bonnet off and tape the light down in the engine bay so you can see it operating.

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PostPost by: rgh0 » Sat Dec 11, 2004 6:29 am

Keith

2 thoughts on your RH corner problem.

You dont have a low oil pressure cut out switch on the car by any chance ? Right handers is where Elans have oil pick up problems ?

I once had a similar problem on my Esprit that was due to the low tension lead to the distributor have rubbed though its insulation on the engine block. Going through RH corners caused the wire to move and short out once you straightened up it picked up again as the wire swung back and the short stopped.

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PostPost by: type26owner » Sat Dec 11, 2004 8:38 pm

You dont have a low oil pressure cut out switch on the car by any chance ?

Nope.
Right handers is where Elans have oil pick up problems ?

How to I tell that? I'm too much of a coward to take my eyes off road to look at the gauge. Need to find a fearless passenger that doesn't weigh much. :rolleyes:
Do your new tires feel all that much stickier?

I'm pleased to have found these tires and to have stumbled immediately upon a suspension setup that puts me into a very comfortable state where I can go fast without working hard to do it. Tweaking it a little bit has transformed it from an ill handling nightmare into a real road weapon. Already know I can kick a Neon's butt. :D

Have to again credit Rohan for the suspension tweaks and Kiyoshi for the tires. Thanks guys and also to Jeff our stealthy forum poobah.

Rohan, here's how the two types of nozzle deflectors work. It would be bad for instance to have a plume of gasoline similiar to a standing wave shower out of the throttle bodies at WOT if the splash ramp of the whistle where inclined incorrectly. Do you think it should direct a sheet fanned perpendicular across the airstream or inclined further downstream? Intuition tells me to steer clear of the screen mesh type one.
<a href='http://kinsler.com/Cat_31_Web_HTMLs/0201234_screen31.html' target='_blank'>http://kinsler.com/Cat_31_Web_HTMLs/020123...4_screen31.html</a>
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PostPost by: rgh0 » Sun Dec 12, 2004 12:08 am

Keith

I would try to get the fuel stream from the injector to stay in the air for the longest time before it could hit a wall. Once the fuel is on the wall of the inlet its a lot harder to get it to evaporate than it is as a free floating droplet.

The accelerator pump nozzle in the Webers points straight down stream for that reason. So perhaps best if the spray fan from the notch points downstream if that will help keep the fuel in the airstream longer. However given the fancy flow patterns in any inlet manifold you dont really know what is going on, so its really a try it and see exercise

Other things apart from fuel washing the walls that might give you a bore wear problem could be.

Piston temperatures getting up to high or piston clearance to small - is the wear only on the bore or is it on the pistons to.

Rings gaps to small causing the rings to bind as temperatures get up.

Liner hardness - are you confident of the material spec for the liners you are using

Dust ingestion - do you run filters on the car ? How dusty are the tracks you run on, it does not take much ?

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PostPost by: type26owner » Sun Dec 12, 2004 2:09 pm

I would try to get the fuel stream from the injector to stay in the air for the longest time before it could hit a wall.

We have converged on the key objective. Making up a set deflectors is no sweat but optimizing them to work corectly could be so here's hoping I'm lucky. Expecting to have to reduce the overall rate of fuel consumption across the entire rpm range but that I know how to do. It's a trial and error process which is a pain in the can to do but fortunately not dominated or impacted in anyway by two-phase flow.

The pistons are J&E's latest trick ones which require only .0035" clearance fit in the cylinders. Discussed the best practice procedures with the J&E application engineer and applied those recommendations.

We built our own airbox which uses a paper filter element. It supresses the induction noise enough so we're one of the few cars out on the track that does not run an exhaust muffler or baffles. IIRC, it's been measured at 90 dB only.

Liner hardness - are you confident of the material spec for the liners you are using

Nope, I'm not sure. I was under the impression that there were no choices. Have I errored on this one possibly? The bore of the sleeves just wore away so there was a .005" ridge at the top and it started to slap.

-Keith
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PostPost by: rgh0 » Mon Dec 13, 2004 9:47 am

Keith

I have never done any testing on liner hardness because I have never had any problems with excessive wear but a variation is certainly possible depending on alloying material content and casting / production method.

If you have a sample of your worn liners I would check versus the orginal block hardness to ensure in the same ball park. Grain size and orientation in the metal can also influence wear rates but that gets into some pretty heavy metalurgy.

If your running modern JE pistons and installing with the right piston and ring gaps ( I do he same) then hard to see it being a piston and ring related problem unless you are getting excessive combustion temperatures for some reason ( mixture or spark timing problem) but this should be obvious with other symptoms except bore wear.

Interesting that you run an airbox and paper element on the BRM. Most people dont appreciate the contribution an open inlet tract makes to overall noise. We have a 95 dBa limit at 30m for our open race meetings in Oz and most people run a muffler but open inlets. I always thought some combination of the right level of silencing on both ends was the way to go rather than put it all on the exhaust.

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PostPost by: type26owner » Fri Dec 31, 2004 1:13 am

Fired up the BRM today with the fuel injection nozzle deflectors (whistles) I made up. My brother immediately noted the induction noise was noticably more muffled. For the very first time the throttle bodies were cold to the touch so it's definitely cooling due the latent heat of vaporization now. I've also noted the acoustic effect of having the fuel well atomized before on the DCOEs so having it do the exact same thing on the T-J was not a big surprise. :D
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