poss BCS prob. Help!!!

[cragmaz]

:help:Hi all,

Had a strange problem develop yesterday with my T5.

Normally under full load, about 4/4500 Rpm in 3rd or 4th, at approx 16psi, i get a definate (only what i can describe as) a boost cut, that quite jolts you out of your seat, (like a sudden impact with summat) and is very scarry!!!!

Been on the dyno today to check the fuelling, boost, etc, etc, and all is well, boosts at a steady 1 bar, with afr`s riching to 12`s to the limiter, and producing healthy power and torque figs, but out of about 8 runs, i would say at least 5 experienced this problem.
Car has had recent plugs, cap and rotor, and used to be ££££ on till about a week ago!!!

If you Lower the boost, it dont do it, but 1 bar, should not be a problem, and it used to be ok before this started happening.

We examined the BCS (that was already on the car, since i have had it) and it looks nothing like the spare volvo one i have in my garage, totally diff!!! dunno what its from, its smaller and thinner, with 2 vac. connection points on the top and 1 one the bottom, comapared with the big, chunky volvo BCS with all 3 vac. connections on the same side.
cant find any volvo markings on it either, Can anyone help me please, as its really doing my head in!!!!:help:

Thanks in advance

Craig (V.sad!!!) :cry:

[irf]

it could still be spark blow out. had that on some plugs that were 50 miles old. genuine volvo as well.

the bcs just sounds as if its from a later model which is fine if it is.

[cragmaz]

it could still be spark blow out. had that on some plugs that were 50 miles old. genuine volvo as well.

the bcs just sounds as if its from a later model which is fine if it is.

What plugs should i use, and what gaps???

Using bosch tridium at the mo, gapped at 0.5 as i had a splutter under full load, so i closed em up from 0.7.

Cheers

Craig

[irf]

can only recommend the genuine volvo ones as that's all i've used although there are a few 400bhp cars that use the same as well.

[cragmaz]

anyone else got any idea`s????? (please!!)

C

[Alan M]

When you had your car mapped did the 1 bar boost cut/limiter get removed? It sounds as if you are still experiencing boost cut as with a standard ecu at 15 psi-ish. It may be worth a check. How was it mapped? With an emulator live?

[Jamest5r]

NGK are good plugs, but i have had trouble with Denso plugs before, my GT4 melts Denso plugs in a few hundred miles at just over 1bar (very luckly without causing any engine damage). NGK plugs last for ages at the same settings where Denso plugs didnt.
I spoke to a tuner about this and he said he has seen this problem before with Denso plugs and doesnt like to rolling road any cars at his place unless its got a brand new set of NGK in it!!

I now have NGK Iridium +8 in the GT4, they are very good once engine is warm, but run a little rough when cold. In 850 T5 i use standard Volvo plugs with my Rica 280 no problems, the standard plugs stay like new, run without hesitation and last for ages.


--------------------------------------------------------------------------------

Jez

850 T5
Auto

Found this for you mate, personnaly i go for NGK R BKR 7EVX

[cragmaz]

When you had your car mapped did the 1 bar boost cut/limiter get removed? It sounds as if you are still experiencing boost cut as with a standard ecu at 15 psi-ish. It may be worth a check. How was it mapped? With an emulator live?


thanks for that mate, will have to check that out, dint know they had a boost limit.
could it be the bcs by any chance??

cheers
craig

[Alan M]

If its working fine up until this point I would suggest your BCS may not be at fault. Can you try another in its place?

[p fandango]

thanks for that mate, will have to check that out, dint know they had a boost limit.
could it be the bcs by any chance??
its not actuallly a boost limit, 850's don't measure boost. The ECU has a preset % of air passing thru the MAF at set rpm steps, if you exceed it then the ECU cuts the ignition quickly (the jolt you felt). So even running an MBC/EBC the MAF limit still cuts in, does on mine

with this standard safety feature i've never been able to figure out how people claim an MBC will bend con-rods (not that its a good idea to be cautious anyway)

[cragmaz]

its not actuallly a boost limit, 850's don't measure boost. The ECU has a preset % of air passing thru the MAF at set rpm steps, if you exceed it then the ECU cuts the ignition quickly (the jolt you felt). So even running an MBC/EBC the MAF limit still cuts in, does on mine

with this standard safety feature i've never been able to figure out how people claim an MBC will bend con-rods (not that its a good idea to be cautious anyway)

Ah,that sounds like exactly whats happening!!!

How can it be sorted (if at all)???

Thanks in advance

Craig

[p fandango]

Ah,that sounds like exactly whats happening!!!

How can it be sorted (if at all)???
tbh i don't know of any ways to fool the MAF sensor, so its either lower the boost down a bit or get a remap which will have a higher MAF limit (any remap will have a higher MAF limit). HLM used to offer what they called a "DIY map" which raised/removed the MAF limit & the RPM limit specialy for us MBC/EBC boys without altering anything else on the map. Might be worth seeing if he can still do that

[cragmaz]

tbh i don't know of any ways to fool the MAF sensor, so its either lower the boost down a bit or get a remap which will have a higher MAF limit (any remap will have a higher MAF limit). HLM used to offer what they called a "DIY map" which raised/removed the MAF limit & the RPM limit specialy for us MBC/EBC boys without altering anything else on the map. Might be worth seeing if he can still do that

Ok will look into that.

Thanks a load bud. really helpful info

Craig