Scottish Elises

Gents,

After my head work I'm getting quite a lot of pops and bangs on overrun, sounds fantastic and makes me smile, but the Larini isn't going to appreciate it for long... I'm wondering if it's mixture problems. I'm running a larger TB adn VVC plenum (Still CBA to swop back!) and I have read that this will cause lean running. (No I can't afford an Emerald!)

Any thoughts?

Is there any point in getting a rising rate FPR or an adjustable effort? E-Bay FPR If so what should the base pressure be?

That is a very good price for an adjustable FPR.

I paid over £80 a few years ago for a guageless one, and bought one for Craig last week at £48 for a Skoda, but like that one it is generic, except it was priced for the Elise at £68.

Something to look out for when it is "Buy it Now" for generic parts.

tut

I take it that this may be a good idea then...

Any idea on a starting pressure, 3 bar is standard is it not? Any tips on getting it right?

I'll ask if any NorLOGers have a wideband kit I can borrow.

I am also looking at a pikey ECU upgrade, the MegaSquirt. Anyone got any experience of them?
(Other than a past history in dodgy porn of the same name! )

RICHARDHUMBLE wrote:Gents,

After my head work I'm getting quite a lot of pops and bangs on overrun, sounds fantastic and makes me smile, but the Larini isn't going to appreciate it for long... I'm wondering if it's mixture problems. I'm running a larger TB adn VVC plenum (Still CBA to swop back!) and I have read that this will cause lean running. (No I can't afford an Emerald!)

Any thoughts?

If you drive at 5,000 rpm and then lift right off the throttle while still in gear to coast down towards idle does it pop and bang all the way, or only once the RPM is below 1,500-2000?

If it pops and bangs all the way I would guess that your TPS is dodgy or that the MEMS isn't calibrated for it properly - the old MEMS pedal dance should sort that out. You could prove this by disonnecting the TPS all together.

If it only pops and bangs below 1,500-2,000 RPM then I would guess that it is misfiring on closed throttle and thus letting a load of unburnt fuel into the exhaust. I wouldn't expect that to be caused by it running lean, but rather by some ignition timing problems.

If it only pops and bangs once or twice, just as the revs pass the 1,500-2,000 then this is totally normal - the MEMS engages fuelling for a complete engine cycle before re-engaging ignition to avoid detonating a half-fuelled cylinder (it's all to do with the fact that the injectors are batch driven).

I would revert to a standard diameter throttle for a while and see what impact that has before changing FPR.

Cheers,
Robin

What he said.

Wish I had the time to write replies like that.

Dan@JPS

Cheers Robin and Dan,

It pops and bangs on lift off when cold (V. loud too) and burbles loudly when coasting down when hot. I don't have the smaller TB anymore, it was cannibalised for bits... I do have a TPS sensor somewhere though. I'll do the pedal dance and see if that works then change the TPS.

TVM

Rich

roadboy wrote:What he said.

Wish I had the time to write replies like that.

Dan@JPS

LOL. I type fast, though not always accurately ...

Robin

His bloody brain works too fast though for a normal human being........

tut

To be honest, considering your modifications and the fact that you are still running on the standard MEMS, this sounds totally normal to me. The fuelling is never going to be ideal as the MEMS can only increase or decrease fuelling across the full map. As you are now flowing considerably more through the head at higher revs it will naturally increase the fuelling. You will therefore find that in most cases this will cause it to run rich at low revs and mid-range.

The bangs and pops are due to unburnt fuel and this is usually a sign of runnig rich, rather than lean.

I would just keep an eye on the colour of the plugs and if there are any signs of running lean either buy an FPR or adjust the standard one.

HTH

Dan@JPS

when you say adjust the standard do you mean squash it in a vice?

Actually you can squash the standard FPR to increase the pressure, but hit and miss, so would not recommend it.

tut

RICHARDHUMBLE wrote:when you say adjust the standard do you mean squash it in a vice?

Yes - there is a section on the emerald website in Dave's articles bit that describes him doing it - he used an air line and a pressure gauge connected at one end to measure it and then two sockets in a vice to do the squishing IIRC.

Actually I am just starting to work with Lawrence's wide band lambda kit which has an RS232 logging output (I think, we haven't yet used that part of the circuit) that can feed either palm pilot or laptop and can capture RPM, throttle angle and lamda. You could use that on your car to figure out what was going on, if you're prepared to do a bit of choppery on your wiring loom.

Cheers,
Robin

I'm off to the monthly meet of NorLOG tonight (Get us all organised!) I'll see if I can blagg one there thanks anyway!

I'm looking at thei MegaSquirt ECU thingy ATM. Looks promising, the kit is £165 and it can control spark and fuel, thie bits I don't know (Exposing major flaws in my ECU knowledge!) are:

Does the MEMS have anything to do with the spark (Early car with dizzy)?
Do I need sequential fire injectors or will bank fire work OK? (MegaSquirt only has 2 drivers but the bumph says bank fire is fine)
How does MEMS interact with the immobiliser?
Can I be bothered to find out if the MegaSquirt will work with a K?

Ta
Rich

with regard to Megasquirt - it can be a bit hit or miss. Some engines it works well with, others it's more trouble than its worth. It seems to work well with big V8s for example

Not sure how it shapes up in a K - the K's reasonably straightforward so I imagine it'll work

Ta

I'm slowly pulling the data together...
The K uses bank fire 1-4 2-3 the VVC uses fully sequential. First problem solved....

Now looking at the Crank position sensor...