Boost check

[g-dub 0]

after my Q/A on the boost noise, i'm still not getting any noise, put my hand under the butterfly on the throttle and can feel air being expelled, but no satisfying noise, also the car doesn't seem to pull like it used to, after all the simple mods iv'e done it actually seems alot slower than standard, what things could i check, the charger makes loads of noise so one assumes this is ok????? how can i check for boost leaks???

[W3RKD 0]

http://the-corrado.net/.archive/forum/viewtopic.php?t=17067

[g-dub 0]

tried this can't find any boost leaks, and still seems slow, i mean it's quick but although noiser seems just a little bit quicker than the 8v taken out,any other ideas peeps, heard that the vacume hoes that goes to the ecu is exactly a mtr long and must be, if this is shorter would that make a difference??

[h100vw 0]

If the hose is too long or short it'll bog down and generally be nasty to drive. The power will be on/off like a switch. Usually they pull ok at high revs but badly on WOT at low revs.. You can get away with about 5cm either way before it starts being really noticable.

Gavin

[g-dub 0]

well its not runnn nasty just ain't quick, dissapointing really, but i know the vacume hose has been shortened, so you say this could be it,if more than 5cm has been taken off, keep my fingers crossed,

whats does the vacume hose do??

gonna buy a boost guage and check the boost that way as well me thinks, is it supposed to be 11psi?

[h100vw 0]

10PSI would be ok for a std pulley. The ECU uses the pipe to sense the pressure in the inlet manifold. Depending on throttle postion, this could be positive, on boost or vacuum, off boost.

 

Each inlet valve opening and closing causes a pulse in the manifold, these pulses travel up the vac pipe and they will be out of phase and confuse the sensor in the ECU (it's name escapes me.) :roll: Finally got it MAP sensor... Manifold absolute Pressure.

 

Without the pipe on it'll assume there is no load and it'll struggle to accelerate at all. Likewise any leaks in that pipe will have a similar effect as the ECU will be looking at the wrong place in the stored maps, for the conditions that prevail.

 

If you were to shorten the pipe to 50cm it should be ok and if you lengthened it to 1.5m same deal.

 

The same principle is used with 4 branch manifolds to extract power at certain rpm ranges. A 4-1 has different characteristics to a 4-2-1. The diameter and length of the pipes also have an effect.

[g-dub 0]

cool, explains in my language cheers, i also have the 4-1 manifold, so should i replace the vacume hose with a new one off the correct length

[h100vw 0]

I would replace it. It doesn't cost much in the scheme of things. I'd replace the other hose too. That goes to the carbon canister. Any leaks in that area will trip up the ECU.

 

Gavin

[g-dub 0]

right then, relpace the vacume hose going to the throttle with one from a 1.8 16v hope this is the correct size, but still no joy was nearly double the length of the one i replaced though!!, also have removed the carbon cannister, blocked off all those pipe or should they have gone else ware??

[W3RKD 0]

right then, relpace the vacume hose going to the throttle with one from a 1.8 16v hope this is the correct size, but still no joy was nearly double the length of the one i replaced though!!, also have removed the carbon cannister, blocked off all those pipe or should they have gone else ware??

 

luke..

give me a call as i have just had an idea somthing the guy who fitted the engine may of overlooked..

[g-dub 0]

when now or tomorrow??

[W3RKD 0]

now if ya like usal number. :lol:

[g-dub 0]

still no luck, could spark plugs cause a problem as i used a set of ngk ones that i had lying around, instead of thr wd-thingys

[h100vw 0]

Maybe, get yourself some W6DPOs. Cheap on ebay at £20 plus postage. a tenner each off gsf.

Gavin

[g-dub 0]

got a set of bosch ones in the head i bought there brand new so will try them, it got worse today, a vauxhall chavaler overtook me today and i could even catch up :oops: