1983 Elford Turbo

[gt_james]

Be careful under WOT, if its missing from lean, and under boost you can quickly damage the engine. start rich and work leaner, not the other way round.

I've not set up an elford turbo, but I jetted my weber on the road with an AEM wideband (and then finished off on a dyno). Tune idle, and cruise/part throttle first on the webers, and start rich, working leaner. Then when I did try tuning WOT I kept it in 3rd or 4th and left foot braked whilst accelerating to keep it under load but going slower so I could actually read the gauge at different points in the RPM range.

I think dyno is the only real way to tune WOT on a carb, unless you can datalog.

[ian65]

Be careful under WOT, if its missing from lean, and under boost you can quickly damage the engine. start rich and work leaner, not the other way round.

I've not set up an elford turbo, but I jetted my weber on the road with an AEM wideband (and then finished off on a dyno). Tune idle, and cruise/part throttle first on the webers, and start rich, working leaner. Then when I did try tuning WOT I kept it in 3rd or 4th and left foot braked whilst accelerating to keep it under load but going slower so I could actually read the gauge at different points in the RPM range.

I think dyno is the only real way to tune WOT on a carb, unless you can datalog.

Exactly this....
the last thing you want to do is lean it out under boost, I've always run my Elfords a little bit rich with no ill effects.

[gt_james]

The AFR numbers I posted as a target are for NA also, for turbo you need to go a bit richer under WOT. Although at the boost levels of an elford its not as rich as a more powerful set up would need to be set at.

[Moomin]

It's been a minute or two since I've posted an update.

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Engine out for a new clutch release bearing, but change entire clutch assembly. Glad I did as it had the 215mm clutch which had been rubbing on the flywheel, 225mm fits perfectly.

I also got fed up a couple of month back of the Elford manifold constantly not sealing so I made a new one, complete with turbosmart wastegate

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Made a huge difference in turbo spool, and it made 7psi at 4000rpm and wastegate opened, which was daft so it's now got a 10psi spring in which it only opens at WOT at 7000rpm

I also machined the SU needle in the mid range last week to try and get a much safer AFR, happy to report it now doesn't climb above 14.2 and cruises at 13ish. Seems a lot happy. Next up is to bin the original back box, I hadn't realised just how restrictive the design is inside it also rattling like crazy.

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Much love

[gt_james]

Your AFR numbers are still not right.

You want leaner at cruise, 14 - 14.5

You want richer under acceleration, 12.8-13.2

under boost you'll want to be richer still, probably 12-12.5 at the low boost level of an elford. For over 12psi I'd want to see in 11s, and really high performance high boost stuff you need to run richer still.

14.2 in boost seems way too lean to me.

Get it set up on a rolling road. What is your fuel system?

[Moomin]

More needle sanding starting with a another BFS needle, 14 to 14.4 on cruise, wide open into low 13s sometimes into the 12s. Annoyingly 11s on idle

Back box deleted and replaced temporarily with a motorbike silencer I had in the yard. That's made a huge difference to the turbo spool speed. Original had completely disintegrated inside. It's going to an exhaust shop for a 2.5" turbo back exhaust later in the month.

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I've also spent the day carpeting the inside rear

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[Moomin]

Fuelling confusion continues although it might not be fuelling.

So I've modified the SU to accept an 8mm fuel barb. Drilled carb fuel inlet to 6.8mm and tapped to M8, fitted fuel barb so hoses ID is same from tank to carb.

I also drilled the float inlet to 3.3mm which is as big as it'll go without running into the float needle not sealing.

Why?

Because I'm running into fuel starvation at WOT, before I modified it you could go WOT 1st, 2nd to 7000rpm with the wastegate crackling above 6000rpm, but when you then hit 3rd it would stubble and then fall on its face.

Now you can get into 3rd a bit more to about 4000rpm before it happens, so I'm thinking fuel pump can't refill the bowl. I've read every thing in the internet but it's all A-Series boat anchor minis that just aren't really comparable in the amount of air shifting through the engine as a turbo rotary at 8000rpm!

Im running a facet cube pump, I'm of the opinion it's just not flowing enough volume to keep up.

There are SU float bowl extensions which would add a bit more volume but they add depth which means more fuel but below the pickup? Can't see that being of benefit.

My thoughts are this, replace the pump with a high volume low pressure pump. See if that fixes it, if not I'll machine up a new float bottom on the cnc mill which adds width rather than depth.

Opinions and suggestions?

Here's a picture of the heap at RADwood this afternoon.

Much love rotary lovers x

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[kenwhiteside]

How much boost are you running?

If you’re worried about the pump perhaps put a gauge inline and see if the pressure drops. I assume you are running returnless?

SU’s are sensitive. I put a bell mouth inlet on mine and it was leaning out terribly over 4000rpm. You should be able to get it working, there is a good post somewhere on Rx7 club with a chap running one at 1 bar. Perhaps you need to get it dyno tuned by an SU specialist.

Final thought. What spring are you running in the carb?

Tim

[gt_james]

Facets are weedy, get a real fuel pump

[KiwiDave]

In-depth technical feedback there James