"spitting" during gear change.

[scubaruss]

Hi...I've been having a problem ( as I see a few people have ) with my SE Turbo burbling & popping on the over-run. Booked it into my local Lotus garage & problem seems to have been cured however.....there seems to be a second problem as the car now seems to "spit" during gear changes - this is the best word I can think of to describe the sound.

So...accelerate or de-celerate, dip the clutch, change gear release the clutch & then this spitting noice. Something else to add...dosen't seem to do it after hard acceleration I.E under turbo boost conditions.

Lotus say the set-up is perfect & the car seems to run perfectly - any suggestions?

[chris.t]

you will find that there is a bit of waste gate flutter during gear changes or decelleration after hard acceleration. Doesn't sound like a spitting noise though???

[scubaruss]

This waste gate flutter....presumably this is a mechanical movement? If so, I have to say the more I hear the noise the more I think it's a mechanical noise but it is quite loud....almost like a mis-fire but just not a pop.

I must apologise for the vaguness of my descriptions...I love driving my car but have very little idea of how it works

[scubaruss]

For anybody who's interested.

This has been driving me nuts so I've been trying a whole host of things to try & cure it . I think I've found the cause of the problem but I still don't understand why it's happening.

It seems that the use of premium fuel ( optimax ) was causing the problem. I've reverted back to normal un-leaded & the problem seems to have gone away. Can anybody offer an explanation for this

[robp]

hi, I only ever feed mine full fat optimax, and after a couple of tanks it felt alot happier. I'm not sure how high up the food chain you can go with the stock computer, doubt it would cope with the 108 ron specialist stuff. anyone know?

[chris.t]

the waste gate flutter is quite normal and from my experience the noise will vary from a gentle flutter to a slightly louder whistling flutter if you have a bbr conversion and the turbo is blowing up to 1 bar. Get it checked out if you're worried though cos i'm no expert.

[TheBard]

Hmmm, if it sounds like a catherine wheel ('pfft, pfft, pfft" several rapid spits in quick succession) its just the boost pressure from the turbo pushing back through the system as boost tries to escape during off accelerator moments... I love the sound as it means I'm accelerating nicely and roaring up the gears

If you're an NA owner, or know that it isn't air coming back through the turbo, then can you tell us if it comes from the front or back of the car? Is it exhaust related, or engine? Is it louder on the left or right side of the car?

Good luck,
Ian

[scubaruss]

From the investigation work that I've done I'm confident that it's coming from the exhaust but from under the car as oppose to out the back. It's had a new back box put on recently so was wondering if it's related....

[TheBard]

Hmmmm, well that quoshes my next thought, as when the cat started to rumble on mine, initially it made a strange mechanical gaspy/spit sound before it started really rattling, but if you've just had yer pipes done then it probably isn't that....

Can you create the effect when stationary?

Ian

[chris.t]

Hmmmm, well that quoshes my next thought, as when the cat started to rumble on mine, initially it made a strange mechanical gaspy/spit sound before it started really rattling, but if you've just had yer pipes done then it probably isn't that....

Can you create the effect when stationary?

Ian

Its an SE so no Cat. if you're up for it scubaruss theres a gang of us that meet every month near Alton (See Southern Area Meet, under UK events). Some of the guys come up from your way - i'm sure one of them would be able to give you a good indication

[ESM]

Are you sure its a problem. The Elan has a straight-through exhaust even in stock form. The relatively unbaffled exhaust means you hear things you might not in other cars - it gets even more noisy with aftermarket systems though. The 'spit' could just be from a fluid flow effect related to the ECU cutting fuel on the overrun and not evidence of a problem at all.