legacycentral bbs

Interesting topic this fuel pump discussion.
>
> Racing a 92 Legacy Turbo, and the last race (Canadian Rally - Big Horn
> Alberta) had us fighting a nasty intermittent ignition/fuel problem that
> caused no end of grief during the services, but only affected the car once
> on course costing 30 sec. We also ended up warping the passenger side
> manifold (again), causing a large exhaust leak between manifold and the up
> pipe (stuffed it with folded metal, used heat shield to hold it place).
> We still did very well, but I was at a loss to know what was happening.
> The previous owners indicated they had a similar problem and when they
> replaced the fuel pump the problem went away.
>
> We are running VP race fuel (103 unleaded) mixed with 92 pump gas (40/60).
> Boost was controlled by a controller I built similar to the one on
> Autospeed.com. Worked very well, the initial spike went to 17 psi then
> back to 14 psi. This actually worked very well, but I am guessing the car
> was leaning out since the heat is warping the manifold. No other signs of
> leaning out -plugs were a little carboned even. Car showed no signs of
> detonation while running - but the warped manifolds. Within the rules,
> fuel system is open, so upgrading the pump and injectors would be no
> problem - problem is we can't run an intercooler. We are also cursed with
> a 32 mm restrictor - car was an absolute rocket without the restrictor
> during testing - easily as fast as a stock WRX - or so it seemed. The
> boost controller worked awesome, and the spool up was fantastic!
> Restrictor turned into a dog - just too much weight for the power
> available.
>
> Knowing all this, what would you guys suggest as an upgrade? Ideally,
> Subaru sourced part numbers would be great (STI) or the overseas RS pump,
> just for ease of install. Do you think this would be enough, or does the
> Holley / Aeromotive FPR the only way to go? The car is less and less
> competitive at events in production-4 against the newer WRX's in the same
> class (we still beat some of them though!) - so we don't want to throw too
> much money at it.
>
> Any suggestions would be most helpful.
>
> Rabin Rutten-James
> ISC Help Desk
> Phone: (9)798-8000 or 8-8000
> Fax: (306)787-4617
> <mailto:rabin.rutten-james@isc-online.ca> rabin.rutten-james@isc-online.ca

The manifolds are cast, so something is definately amis.....they simply
should not be warping at all.

As for the bosot controller, I would redo it, or just get one of the manual
units (or prefereably an electronic one depending on budget) as you should
not have any spike at all...it should simply get to your desired boost level
and stay there.

There are lots of fuel pump/injector combos you can run, but given that you
are not running into detonation issues from the sound of your plugs, doesn't
seem like you need it yet. What you probably did run into is fuel cut
however at that boost level

Is water injection prohibited?

I cant believe you are running 14 to 17 lbs boost without an intercooler! I read somewhere about drilling and taping the fuel rail to even out the fuel pressure in the cylinders, could this help?
Mark

a better idea would be to redo the fuel lines and ensure the regualtor is in the middle, assuring equal pressure to both sides...but as long as you are in there, mind as well get rid of the stock injectors as well

Adam
Z-1 Performance
www.z1auto.com
(631)254-8277

You're problem isn't fuel. You're problem is ignition timing. Are you using a factory ECU? If so, the factory ECU bases its timing curve on air flow through the MAS sensor. If you have a way to advance the timing, you can problably bring down your EGTs, thus avoiding the warped manifolds.

Do you know what air/fuel ratio you are running under wide open trottle and part throttle?

Gary Grahn

Seems like Subaru has a habit of providing just enough fuel pump for
the stock engine and that is all they provide . I have seen several
cars that have benefited greatly from a high volume pump. I say
volume because that is what is lacking. This can be seen with a fuel
pressure gauge and it will fall off at high boost and high rpm's the
pump just can't supply enough fuel. But in your case I am not real
sure that this is the problem, a 32mm restrictor is very small and if
it makes the car a real dog it could be running very rich as the fuel
management system has to be going crazy with this restrictor. Could
you be dumping fuel into the exhaust manifold where it burns and the
heat causes it to warp?
AL(CO)

I don't think we would be dumping unburned fuel into the exhaust manifold -
it would never be able to stay and burn because of the exhaust velocity.
(besides lean AFR burns hotter than rich AFR doesn't it?)

To add more to this debate - this is the third time the manifolds warped,
the first time happened before we even raced - caused an engine fire. It
was fixed with multiple exhaust gaskets (I never did it). They blew out
near the end of the first race. I fixed it with a custom shim I machined
out of 3/4" plate steel (double tapered) with a die grinder, angle grinder
and a hand file.

This again blew out the gaskets leaving an even bigger gap the following
race. Screw this - new everything. Both manifolds, crossover, and up pipe.
Lasted a few races, but this last one warped it again. Up until the last
race - we were running 11 psi and under - ALWAYS with the VP race fuel mix.

I thought for sure it was a design flaw in the casting until this fuel pump
discussion came up. This last race had a bizzare ignition gremlin that
would cut power at any sign of boost - even at idle when you give it sharp
jab and the boost needle barely moved. We'd reset the ecu (kill main power,
wait, then re-engage) and pray. Always acted up in the pits, and in
staging, but only once in the race. John Paynter (previous owner) said they
chased a similar bug that went away when they changed the fuel pump. They
also never warped an exhaust manifold. They ran higher boost than we did,
but they used pure C116 VP Race fuel (leaded). The ECU coded the pressure
sensor switches (and the MAP) - even when everything was stock.

If this is engine management getting fried with all the wacky changes -what
would be a good solution? Car is definitely faster with the mods - bone
stock boost is terrible.

Any thoughts for a fix?

I think you have bigger issues. there is something wrong somewhere else. If John had similar problems there is more then your mods to deal with. I have never heard of anything like this. Byron has suggested checking your cylinder heads to make sure they are straight, and to make sure the new exhast manifolds are straight. they should match up nicely before bolting tight.

What I dont understand and never have is why you need the custom shaped gasket on a stock exhaust system (at least till the turbo...)
Mark

"lean AFR burns hotter than rich AFR doesn't it?"

They burn the same in the exhaust manifold, both shown as high EGTs. What does your fuel pressure look like, under the conditions of warping a manifold.

Hi Gary (everybody),

Unfortunately, we don't have the fuel pressure in cockpit (or under hood (adding to wish list), so I have no idea.. (really want to now - even just under hood while we're in service)

Any idea the best method for plumbing it into the cockpit? Can you just tap into the fuel rail? Would it change anything too much running a line into the cockpit for the gage? Is it better to have an electric pressure gage?

EGT's have to be the cause of the warping, so having an EGT gage and AFR should tell me what I need to know. What are the suggestions for locating the sensors - I've heard before and after turbo - I assume it would be better before. Any tips on kit's / home made set ups?

Since the car is breathing through the 32mm restrictor -do you think it is possible it is actually rich? By reaction is to think boost is boost - and if there is 14 psi in the engine, it doesn't matter what the restriction is.

Thanks to everyone for all the info!

I wouldn't run a fuel line ito the cockpit under any condition the
risk although slight isn't worth it. A good electric model should be
used. I would also invest in a EGT gauge, the heat warping the
manifold is being developed somehow. Opinions differ on where to
mount the sender for the EGT but I have some temperature figures that
came from a very good source. 1100 cruise, 1300 mild acel., 1500 hard
acel.,1700 1/4 mile drag race all before the turbo and approx 350
drop after the turbo.
AL(CO)

Definately get a good fuel pressure gauge: the GReddy ones are excellent, come with everything you need excpet a guage pod, and have some overstocked ones (blck face only) 52mm for $100 shipped.

GReddy also makes a very nice EGT gauge: $170 shipped, again, comes with everything except a pod to mount it in. The probe should be installed into the exhaust manifold about 2-5 inchesd from head in the number 3 runner (passenger side, closest to firewall). It reads in C (no F is avaialble) and readings will vary based upon setup, gas used, etc.

GENERALLY speaking, you should see around 400-500C at idle, about 700C at crusie at 3000 rpm. When tuning, we use a combination of A/F (via our wideband Horriba), EGT, adna datalogger to measure timing advance and knock. For a street car on premium fuel (93 octane) we look for a very fast rise from 400C-700C as we accelerate in thrid gear, foot to the floor, then a slow and steady rise from 700C-800C. For race gas, you can tune to around 875C-900C. The trick is not to watch EGT alone, but to basically be leaning the car out via some form of fuel controller until such point as timing retard is induced, then up the fuel cirve back about 5%-10%

Adam
Z-1 Performance
www.z1auto.com
(631)254-8277

Couple of things:

You can't run a mechanical Fuel pressure gauge into the cock pit. Very against the rules. You'll need an electrical of some sort. Autometer works well. You can tap the fuel rail, that would work. I would say you can tap the fuel filter, but Subarus have really ancient style fuel filters.

You can get an EGT from Summit Racing or Jegs (same with the FP gauge). Tap it in the elbow after the cyl head, right before the turn. Put it in the manifold that warps the most. If you put the EGT after the turbo, you won't get a good reading because the turbo and the iron before it are absorbing the heat which you need to read.

A/F gauge. You get what you pay for. A $50 Auto meter will not read as well as a $300 GReddy which will not read as good as a $650 Widebad FJO. Your choice. Make sure it has numbers though. You're target A/F ratio will be in between 12.0:1 and 12.5:1. Also, keep your EGTs below 800 degrees C. Anything more and somethings wrong.

About the restrictor. Yes, it will effect your boost. The whole reason its there is to make your turbo more inefficient, to lower HP so its a killer B car. You may want to lower your boost (if you have no fuel control) and see what that gives you.

Later,

Gary