Flat as a pancake

[pwd95]

I've just had my shiney polished plenum chamber fitted. First problem It's as flat as a pancake in the power band 4k rpm to 6k. It used to go like stink in that range coz it's got a Mark Adams chip and big valve heads. What on earth could cause such a vast difference. Second problem it refuses to idle. It's a hotwire 400. Help

[number 7]

Did you take the throttle disc out when it was polished? Possibly not refitted properly, not getting full throttle?. Don't know whether an air leak between plenum and base would cause a flat spot?

7.

[blaineuk]

sound like air leak to me, try spraying wd4o around joints/connection while engine is running, if revs pick up then it is sucking air in that area

[pwd95]

An air leak would cause the engine to not idle and loss of power would it?
I've got a good mind to re seal the chamber, what sealant is the best to use then?

[wedg1e]

pwd95 said:

An air leak would cause the engine to not idle and loss of power would it? I've got a good mind to re seal the chamber, what sealant is the best to use then?

IIRC I used blue Hylomar.

[dickymint]

Like number7 said have you disturbed the butterfly valve and throttle linkage settings?
Stepper motor on them hot wire thingies isn't it?

[number 7]

wedg1e said:

IIRC I used blue Hylomar.

Ditto.

7.

[350matt]

blue hylomar will eventaully dissolve with exposure to fuel, I'd reccommend the Red Hematite type as thats impervious to fuel

Matt

[pwd95]

Heres a few pics;


If the throttle bits need adjusting is this the bit I need to get set up correctly? so that the ECU knows its getting full throttle etc?


>> Edited by pwd95 on Thursday 1st December 14:12

[number 7]

350matt said:

blue hylomar will eventaully dissolve with exposure to fuel, I'd reccommend the Red Hematite type as thats impervious to fuel Matt

Slightly puzzled: on the pack it says "resistant to fuels and lubricants". Can't say I'm familiar with the intricacies of the airflow inside the plenum, but as the injectors are downstream from the plenum base, how could it be affected by fuel?

7.

[gsx600]

Sorry it's not running correctly, -at least it looks good

Before you took the old one of did you measure the voltage on wires coming out of the point you have arrowed ( throttle sensor) - lhs front of plenum, as you would then need to set up the new plenum chamber the same way.

Idle is probably an air leek as suggested earlier

Cheers

Paul H

[pwd95]

gsx600 said:

Sorry it's not running correctly, -at least it looks good Before you took the old one of did you measure the voltage on wires coming out of the point you have arrowed ( throttle sensor) - lhs front of plenum, as you would then need to set up the new plenum chamber the same way. Paul H

My mechanic mate did the job in his garage, I don't think he did this.
Any more info chaps?

[dickymint]

Wyn Page 21 www.pixeltechnology.co.uk/wedge/maint_fuel_injection.pdf

But the throttle plate gap needs to around 0.002"-0.005" not Zero gap.

[v8 racing]

Out of interest is the induction pipe as what you had before or is this new? the reason i ask is because it is heavily convuluted, and this can seriously upset air flow into the plenum?

[mikeb]

ACT sells a very nice Samco type silicone induction hoses.....

The throttle pot would have to be adjusted with the screws that hold it in position on either side to read the same voltage as the old plenum, you can't just take it off the old plenum and just plonk it on anyhow on the new one, especially as you have a modified Mark Adams ECU jobbie setup to read the throttle pot in its old position.

MIkeB

[pwd95]

v8 racing said:

Out of interest is the induction pipe as what you had before or is this new? the reason i ask is because it is heavily convuluted, and this can seriously upset air flow into the plenum?

Yep same pipe. If I put the old chamber back on will it revert back so we can check readings then? Or shal I give it to someone who knows what their doing as is to adjust

[Gandalf]

Sorry to hear about your troubles Wynn - not being too bright in the spanner department I dont have any words of wisdom for you I`m afraid but hope you get it sorted soon mate

[pwd95]

Gandalf said:

Sorry to hear about your troubles Wynn - not being too bright in the spanner department I dont have any words of wisdom for you I`m afraid but hope you get it sorted soon mate

Thanks Steve, I'm going to pull out all the stops to try and get it sorted for the xmas bash. The funny thing is it feels more responsive down low but then the 'power band' just isn't there

[mikeb]

If you have unscrewed it from the old plenum to fit it onto the new one before taking a few resistance measurements then you may have been a bit hasty.

You will then have to take it to somebody to reset the position of the potentiometer. You also gotta check the butterfly travel makeing sure it ain't catching on anything and that all of the connections are air tight.

MikeB

[pwd95]

Allrighteethen, I'll be on the blower in the morning. Thanks all for your help.