17 replies to this topic

[IainNeon91]

Problem:
As title i am experiencing quite a strange flat spot. Im doing about 50mph in 4th around 3000 revs on half throttle, put down the throttle another 1/4 (currently at 3/4 open) it doesn't go any quicker at all, can't get anymore than 50mph. Then i put my foot flat the floor (throttle fully open), lags for a second, and pulls to about 65mph. Idles fine, 1st 2nd gear pull fine.

What I've changed and checked:
I have got the car timed and colour tuned spot on (before problem started). All electrics working as they should. Checked spark plugs, number 1 was a light brown/grey colour, number 2 was a dark brown, number 3 was quite carbonated (black), number 4 was a light brown.

Spec:
998, stage 1 kit with HS4 (AAU needle),1 3/4" exhaust and a sponge pancake air filter.

Thoughts on what i could change..?;
I realise that the pancake isn't doing me any favors with top end performance, so i will be getting a K&N cone. Could i do with a needle with a thinner 'top end' profile? AAA? Or could i just make the turn down the mixture, making it richer? I'm currently sat at around 10degrees advanced on my dizzy, do i advance it a little?

Other useful things to know:
Should i just keep it the same until i do my rolling road session booked in March..?

If you require anymore information i will try my best to answer. This isn't bothering me that much, just sometimes confused about why it's happening and any advice from you Pros' will be very helpful!

(Sorry about the lengthy thread )

Iain.

[jb93]

I'm not really the person to give any advice, as after hours of messing, I gave up and got it rolling roaded

[IainNeon91]

Just thought i'd try and build up my knowledge a bit, for future reference. Whatever happens im defiantly getting some Peter Baldwin magic!

[jb93]

Just thought i'd try and build up my knowledge a bit, for future reference. Whatever happens im defiantly getting some Peter Baldwin magic!

Yep it tought me how much stuff you can lose down the back of the carb

The rolling road was well worth the money though...

[callum2464]

do you have an exhaust blow? because mine does just now and lags alot at bout the the same time, my mini is struggling to get ove 80 and it used to do just under 110 didn't realise untill now how much of a difference good back pressure in your exhaust makes to the performace of your car

[IainNeon91]

No i don't have any blows in the exhaust system, for some strange reason i've gotten into a habbit of constantly checking for blows. Probably because of the amount of trouble i was having with that s***** standard system!

Edited by IainNeon91, 11 January 2013 - 06:58 PM.

[IainNeon91]

The exhaust colour is that light'ish grey colour. Apparently indicating a correct mixture, but i don't know how rich you should run with a stage 1 kit??

[jaydee]

Could be either lean mixture or poor timing.
Try an AAA needle and set it at 2.5%-3.0% CO at idle with a well warm engine.

[IainNeon91]

I will try this! When i next get paid Sorry for the noobie question, but what do i need to do to measure the CO?

Edited by IainNeon91, 12 January 2013 - 08:46 AM.

[cal844]

Sorry for the noobie question, but what do i need to do to measure the CO?

mot emissions machine is the easiest way if you work in one

[IainNeon91]

Sorry for the noobie question, but what do i need to do to measure the CO?

mot emissions machine is the easiest way if you work in one

I'm afraid i don't I made the mixture richer by a flat yesterday and done it again today but it doesn't seem to be making a difference...

[jaydee]

It wont make a difference if the needle is wrong..unless you set it way too rich (to the point you have really sooty plugs, and thats not reccomendable).
What oil in the dashpot?
You need a richer top end needle and to advance the timing a bit.

Edited by jaydee, 12 January 2013 - 07:31 PM.

[IainNeon91]

Ok, so i will invest in a richer top end needle (Any suggestions?), advance the timing and buy a cone filter.

I use 10w40 in the dash pot.

Edited by IainNeon91, 13 January 2013 - 10:06 AM.

[jaydee]

Try something thicker like 15w40 or even 20w50 in the dashpot, this will only affect pick up and accelaration though, for full power you need to try something like an AAA needle.

[IainNeon91]

Will just putting in the different oil noticeably make a difference, without the AAA needle?