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Old 27th September 2010, 09:15 AM   #1 (permalink)
200MPH
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Oil Surge = Misfire?

I'm having trouble sorting out a couple of things in my GT40 motor, which I'm starting to thing are related. I use my 40 for sprints and hillclimbs. Only three events this year due to trans issues. Not fun.

Anyways, just completed a circuit sprint on the weekend and it seems there is a pattern forming.

1) Motor has oil surge. Always has. It's a 347, with a Boss 302 block and Edelbrock Victor Jr. heads. I've had to fit an accusump to keep motor alive. Presently it has a Milodon road race baffled sump (oil pan) and windage tray. It don't hold oil pressure past about 0.9 g cornering, whereas with some slight suspension tweaks the car is now getting up to 1.1 g consistently and spiking up to 1.3 g on turn in if I'm brave.

2) The other half of the problem I'm having is that the motor misfires coming out of corners, coughs and then clears and pulls happily down the straight. Doesn't happen every corner, but does tend to get worse as the day goes on. Search youtube 200MPH GT40 and you'll see and hear what I'm talking about.

What I'm starting to think is that the oil is getting in to combustion chambers and oiling up the plugs when in the corners. I'm running NGK 6 heat range plugs, whereas I think 7 heat range (colder) should be more suited given the power output (386 RWHP).

Does anyone have any specifice experience in this area they can share?

My next plan is to try a Canton Cobra 302 road-race sump, as the baffling in those is different (diamond design), plus it incorporates an anti-slosh baffle and a crank scraper. Yes, I'd like to go dry sump, but it chews up a lot of room, money, time and adds several levels of complexity I'd rather do without if I could. But I understand a properly setup dry sump system is the ultimate answer. I just can't see why a decent wet sump can't do the job, given that I'm not cornering that hard yet in racing terms. Now if/when I can get it to corner consistenly at 1.3 g and spike up to say 1.5 g, well, then I'd understand, and be very happy too!

Any thoughts on my theory as to why it's missfiring, my next planned sump or am I going completely off track here?

Thanks,
Julian
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Old 27th September 2010, 11:47 AM   #2 (permalink)
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Re: Oil Surge = Misfire?

Julian- can you tell us more about the engine? Carb or FI? Either way could it be a fuel starvation problem with float bowls or surge tanks? Do you run a PCV valve? I had a PCV valve dumping oil into the carburator on hard corners on track days. Only occured after I got sticky track tires.
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Old 27th September 2010, 06:38 PM   #3 (permalink)
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Re: Oil Surge = Misfire?

I agree, fuel starvation. With that type of g load your screwed unless you go with EFI and a swirl (catch) tank.

I have seen my accusump light flicker (35 psi) during an open road race in a corner doing about 110 mph. I also was running 5-20 oil which I will never do again.
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Old 27th September 2010, 08:07 PM   #4 (permalink)
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Re: Oil Surge = Misfire?

Don't think it's a fuel issue. I run 8 stack injection, with a 2 Litre surge tank. Misfire does not occur with sustained accel or just after braking only, only after cornering. No PCV either. Oil fumes go straight to catch can.

I'm thinking oil is surging up the cyl bores and overwhelming the oil rings. I know this can happen with V8's due to their configuration. Dunno!
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Old 27th September 2010, 08:46 PM   #5 (permalink)
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Re: Oil Surge = Misfire?

Quote:
Originally Posted by 200MPH View Post
I'm having trouble sorting out a couple of things in my GT40 motor,

1) Motor has oil surge

2) The other half of the problem I'm having is that the motor misfires coming out of corners, coughs and then clears and pulls happily down the straight.
Hi Julian,

regarding issue 1, you are on the well worn path to realising that a dry sump set-up is, on a total ownership cost and aggravation-minimisation basis, the only way to go. This is such a common progression, and apart from having the engine live longer you get to drop it 2 inches for improved CG. I have lost count of how many bearing replacements and sump revisions, and accusump band-aids I've mucked around with - never again.

regarding issue 2, I think it is highly likely that your fuel system is the cause. Datalog fuel pressure, then you'll know for sure. Another possibility is that your wiring and/or ignition components have a bad connection somewhere that only shows up when they experience lateral accel.

Good luck!

Andrew Robertson, New Zealand
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Old 28th September 2010, 01:05 AM   #6 (permalink)
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Re: Oil Surge = Misfire?

Cheers for the thoughts. What I'll do as an intial check is take a laptop in the car with me data logging the ECU and then try and provoke the misfire to see what is going on. Not easy away from the track however!
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Old 28th September 2010, 01:27 AM   #7 (permalink)
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Re: Oil Surge = Misfire?

Hey Julian, The TSOA is running a Wanneroo day late in October (31st I think). Would be a good chance for testing, despite the mobile chicanes otherwise known as Triumphs. Give me a call and I'll get you on the list... Dave has my number!
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Old 28th September 2010, 02:51 AM   #8 (permalink)
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Re: Oil Surge = Misfire?

Hi, just reading abouit the misfire,and was wondering what type of 8 stack injection you are running. I am thinking of getting a system for an LS1.
Thanks
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Old 28th September 2010, 03:30 AM   #9 (permalink)
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Re: Oil Surge = Misfire?

Dry sump would no doubt fix the oil surge problems as previously mentioned
but if your sump has a good windage set it should not be a problem. I'm not familiar with the Milodon sump. My first thought on the mis-fire was fuel surge
but seeing you have EFI that is unlikely. What fuel pressure are you sustaining?
If you could map it you may see a drop around the corners.
What type ignition system are you using? The miss may be electronic.
Good Luck.
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Old 28th September 2010, 05:14 AM   #10 (permalink)
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Re: Oil Surge = Misfire?

8 Stack is a DC&O setup. They do nice cross ram versions for LS motors also, one of which I've had a close up look at.

ECU is Wolf V500, sequential fuel and spark. Spark comes from 8 coil packs, from LS7 Chev motor, driven by the ECU.

What sort of sumps are all you banana benders running Pete?

Irrespective of misfire, I need to sort out oil surge, as relying on Accusump forever does not thrill me. I was just wondering if anyone else had experience that could point to a link between the two issues. I'll find out...one way or the other...eventually. Hopefully before anything goes bang for a change.
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Old 28th September 2010, 05:50 AM   #11 (permalink)
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Re: Oil Surge = Misfire?

To make a wet sump work at the G force you are seeing needs a trap door setup. Save yourself the risk of an expensive failure and go straight to a dry sump setup. Remember that your oil is inclined at more than 45degrees at your G level.

Something that many people overlook with fuel injection: are there any areas where fuel puddles? A simple thing such as a small recess where a gasket is not flush with the port can create an area where fuel will sit. In high G situations this fuel will "fall" out. You may not think it is a lot of fuel but do your calculations. Work out the area of the crevice and compare it with the amount of fuel injected by one cycle of the injector. It is very easy to double your fuel for one cycle and create a missfire.
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Old 28th September 2010, 06:22 AM   #12 (permalink)
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Re: Oil Surge = Misfire?

Julian
Put a fuel pressure gauge in first, if it flutters its a surge issue.

Does it do it on full tanks.

Is your 2lt surge tank tall or laying down flatter.

Is the return from the engine going back to the surge tank.
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Old 28th September 2010, 08:26 AM   #13 (permalink)
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Re: Oil Surge = Misfire?

Hi Julian

Had a similar problem with the oil surge, (not the misfire though), around fast right hand corners. Stangely not left hand. Anyway cured it by fitting a crank scraper and a Canton sump with the diamond style baffles. Like you I didn't want all the added complexity of dry sump. It worked for me.

Glenn
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Old 28th September 2010, 05:58 PM   #14 (permalink)
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Re: Oil Surge = Misfire?

Quote:
Originally Posted by Roger Higgins View Post
To make a wet sump work at the G force you are seeing needs a trap door setup.
I used the Milodon trap door baffled road race wet sump in my big block chev powered race car and still had to band-aid with an accusump - it's weakness was under brakes rather than turns. Bearing life was not bad but I had no grip and my cornering Gs were pretty low.

Cheers, Andrew
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Old 28th September 2010, 06:37 PM   #15 (permalink)
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Re: Oil Surge = Misfire?

Quote:
Originally Posted by 200MPH View Post
8 Stack is a DC&O setup. They do nice cross ram versions for LS motors also, one of which I've had a close up look at.

ECU is Wolf V500, sequential fuel and spark. Spark comes from 8 coil packs, from LS7 Chev motor, driven by the ECU.

What sort of sumps are all you banana benders running Pete?

Irrespective of misfire, I need to sort out oil surge, as relying on Accusump forever does not thrill me. I was just wondering if anyone else had experience that could point to a link between the two issues. I'll find out...one way or the other...eventually. Hopefully before anything goes bang for a change.
Hi Julian my sump was fabricated by Hi Energy Oil pans in victoria.
High Energy Talk to Jole.

No problems with surge at all but I only do very gentle track days so will not be pulling the G's you are.
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Old 28th September 2010, 09:03 PM   #16 (permalink)
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Re: Oil Surge = Misfire?

Jules drives his car like he stole it. To give you an indication on how hard this 40 gets driven.
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Old 28th September 2010, 09:20 PM   #17 (permalink)
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Re: Oil Surge = Misfire?

Jules,
I run the Milodon rear pick up race sump in my 347 RF.Have a look at that also.Absolutely no issues.Was around US$400- several years back.Dont know price now but $AUS is near 1-1 now.After talking to a number of Ford race guys was fitted for same reason you now have.
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Old 28th September 2010, 09:20 PM   #18 (permalink)
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Re: Oil Surge = Misfire?

Julian sounds like the sort of driver who will use all his car has to offer & then some, dealt with his type before, someone has to grab him by the short n curlies & point out that a dry sump is his only real option..period. Its the old story, you can pay me now or pay me later...but you will pay....!

Its bloody hard to convince me that he is really trying hard when he has time to look at the oil pressure etc, plus there is probably another couple of 'free' HP with the dry sump setup...its win-win all the way...lot better than whine..whine.
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Old 28th September 2010, 10:51 PM   #19 (permalink)
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Re: Oil Surge = Misfire?

Thanks for the comments lads.

I'll probably try the canton wet sump first up, and if that don't work then I know it is dry sump time.

Jac Mac - most of my oil issues I see via video playback from in car camera that captures the oil gauge. But yes, I have been guilty of looking at oil gauge when going round long sweeper and the car has set into understeer. Not much else to do! But that's something else to work on and a whole new conversation. It turns in well, but as soon as you go near the accelerator mid corner it starts to push. Dull...

Either way, I'll post up some results once I've made a change, hopefully in a few weeks rather than months.
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Old 29th September 2010, 03:07 AM   #20 (permalink)
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Re: Oil Surge = Misfire?

Thanks for the info, I am thinking of using the downdraft DC&O set up, but having not actually seen one, it is good to get some feedback about them.
Thanks
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