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ChrisS
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by ChrisS »

Yep, wideband fitted and integrated into the ECU. I did do a small amount of logging, but only on a short trip so it's pretty useless info at present as it wasn't even fully warmed up. I tried dialling in a bunch more fuel in the problem area but it felt the same (and the AFR fell as you'd expect), ditto when I dialled in a load more advance, no perceivable change. I made big changes too, the fact I felt nothing as I switched maps is a bit odd in itself! In the past, I've changed a couple of cells a few percent and felt the difference. This time I added 10% fuel to a great big block of cells centred on the problem area, switched the map and didn't feel anything change. If the AFR hadn't changed, I'd have doubted the switch was working.

(One possible issue with measuring the AFR....I only put a bung in one branch, and the two banks are completely isolated, so I could well have a problem on the bank I'm not looking at I suppose. Not too bad to get another bung put in I suppose).

Mystifying - I've had poor maps before now on other engines and they've run generally OK. It could be way too rich in the affected area so I'll try leaning it out. Aiming for a particular AFR isn't necessarily what the engine wants unfortunately, it needs to hit the rollers really.

After talking it over with a few folk, if time allows after I swap the flywheel and clutch again, I think I've decided to pop the blower on it tomorrow and see what happens - see if the harshness goes away under boost. It's a safe enough map in terms of timing (very retarded) and there is plenty of additional fuel added and timing taken out on boost so I don't think it'll do any harm.

That way I can answer the other big question I have about it - how much boost am I going to get.

I'm sure I'm overthinking this...but that's just me I'm afraid. Fairly described by the engine mapping guy as 'a worrier'!!

More systematic testing required really, it does feel like the basics are OK. It's so sweet over 3k revs, maybe I expect too much lower down....but I don't think so.

Again, thanks guys - appreciate your thoughts on this. Keep 'em coming. I'll report back on how it goes. I guarantee I'll be honest if/when I find out what's wrong - I won't try and hide it if I cocked it up somewhere!



Just saw the EGT question, good call, but I've not been able to yet, I'm waiting for the pyrometer to arrive! One of those tools I've thought about buying but never have until now. Hope it arrives soon as it'll come in handy.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by ChrisS »

Didn't have time to fit the blower after changing the flywheel & clutch again, but did manage to swap injectors - no change.

Now I'm starting to think the problem is apparent at all revs on or off load (just a lot more obvious at 1500-2000)...so either something is getting worse, or I was just kidding myself before.

Reaching the stage where all I can think to do is pull it out, take it apart and start from scratch, assuming nothing, measuring everything, even the most unlikely of things.

Might pay me to just put the 'old' engine back in and just try to enjoy the car for a while. Maybe focus on sorting out the 6 speed gearbox and come back to the engine when the pain has faded a bit!
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by Mats »

Rotor/cap or leads checked?
Did you do the old "wet exhaust" trick? spray some water on the (cold) manifolds and start the car, check if the water evaporates evenly.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by ChrisS »

Thanks Mats.

It's a 6 pole coil wasted spark setup. Could conceivably be a lead or even the coilpack of course, although the last engine ran fine.


Nice idea on the water - not heard taht oen before..but I am waiting for a pyrometer to arrive so should be able to be slightly more scientific with it with luck.

If it doesn't arrive soon I'll try the water trick.

Have yet to try a cylinder drop test. That'll be easy enough.

Grateful for the thoughts.

Cheers

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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by ar4me »

Mats has a good point. Check plug wires. On a 24v with coil packs (not on plugs) in a 75, I had rough running that seemed most notable at low RPM, and then it would come alive. Almost by chance I noticed an intermittent tiny spark from a plug wire to the valve cover. The plug wire did not look damaged, but it had been pinched at some point. Enough for the spark to jump, and obviously, not consistent firing on that cylinder. In the dark, run the engine and watch for any sparks. In my case it was intermittent depending on how the plug wire would move, so play with it a bit. An easy and free check.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by Mats »

I have som issues with the leads on my racecar, they vibrate loose. Sometimes it starts to misfire in certain corners but are fine again on the straights. In the pits I found all leads loose on the dizzy, they were just "kind of" on the cap and moved in the corners. The MSD unit sure makes a good spark. :)

Kind of like when I noticed that 3/4 center electrodes had eroded away on the plugs so that the gap was roughly 5mm, didn't make a difference at all when I fitted new plugs. :shock: :D
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

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Tried another tack this morning. Put a normal map in one slot, and a map with zero fuel in another, then switched between the two as I drove along. Tried with throttle wide open, closed and partial, made no difference to vibration/harshness as I switched the fuel on & off.

...so, I reckon that must mean it's purely mechanical.

Given the compression test results, I think this test has effectively eliminated everything but the principle rotating/reciprocating parts.....?

Engine balance man has asked me to put the old engine mounts back on before we go any further so I'll do that next.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

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...and we're back!

Mounts fixed it. I took the plunge and fitted the blower too - goes rather well.

Only slight issue now...it only makes 7psi of boost, which is puzzling. I was hoping for more like 10psi. I'll check for leaks, then try a smaller pulley, then get it mapped.


...did I say, it goes rather well..... :)
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by ChrisS »

Minor update....prior to getting it mapped properly, I've fitted the inlet runners with WI nozzles just in case it needs some help, and gone with a smaller blower pulley. Drive ratio is now up to 1.97:1 but still only making 9psi. That'll do - it is what it is. I checked for leaks, and apart from valve overlap, there aren't any, so it's ready to go I think.

Certainly driving pretty well considering it's on a far from optimised map, and aside from a minor niggle with the belt, it's all done.

Next update should be with the final numbers after the RR session. I'll advance the cams on the rollers so I can see what that actually achieves in terms of power/boost gains/losses. It'll be interesting if nothing else!

Nearly there...can hardly believe it, and just waiting for something to break :)

Quick question though....crankcase ventilation. I know that putting the oil fume back in to the engine is back in terms of it reducing the octane of the mixture, but how bad, and am I risking poor upper cylinder lubrication by not doing this? (Currently have a catch tank with a filter on it, venting to atmosphere). I also wondered if it would be worth feeding the fumes into the inlet to help improve blower seal? Thoughts chaps?
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by MR2 Zig »

puting your oil fumes into the intake is a power thing. also helps seals to not leak
and it keeps the top of the engine cleaner with no oil mist running about
plumb your oil vapor line in just upstream of your blower. The amount of oil should not have any effect on the blower or upper cylinder lubrication.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

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The only reason it's plumbed back in is due to emission demands.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by Zamani »

What about crank case vacuum?
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

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What about it?
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by MR2 Zig »

as a way of making more power it is "supposed" to make it easier for the pistons and crank to move around...less air in crankcase= less air resistance for things moving in the crankcase.

Could you measure any horsepower increase from using this....probably not.

does it help emmissions...probably.

Does it keep you from ozing oil at every seal....not entirely, but it is way better than positive pressure in the crankcase.

And it keeps the oil vapor from getting messy on your nice clean engine.
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Re: Supercharged 12V/Stratos copy/engine tech type stuff

Post by la_strega_nera »

There's no vacuum in the plennum at WOT - hence, it's not a power thing - it's emissions.
Now, you can use it as a power thing, and alot of drysumped race engines will pull *alot* of vacuum. Downside is, reduced oil mist in the bottom of the motor to help oil the cylinders.
Drag guys use exhaust gas velocity to pull vacuum in the motor - circuit racing organisations tend to frown on this approach due to the oil being pulled into the exhaust. When I was looking at doing it for my Falcon, I was looking at getting one of those alternators with a vac pump built into it that alot of diesels come with.
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