Servere lack of power on boost on c1j

[Markey Mark (BD)]

Got one for you lot which to be honest has got me baffled abit

I had someone pop there car over last weekend as he's been having issues with it lacking in power when on boost so I said i'll have alook as its fitted with a VNT

Now when he said it lacked in power it was an understatement, when its on boost it just doesn't want to go anywhere! My beetle has more power then it! :eek:
Now the basics have been covered by the owner so left them, he's also changed the fuel pump and filter to a know good working one too

Now I thought it was lacking in fuel pressure so I changed the fpr, still the same
I measured fuel pressure on idle and on boost and its all fine

I reset the vnt and it builds boost fine, reach's 20psi easily

Next I pulled the carb off and checked that, found jets too small for the boost so rejetted. Once again no difference
Fueling is obviously leaning out as its not revving up and boosting a lot so this may not give an idea why it won't give power. Even a leaning out 5 can still boost and rev through the rev gauge but not this one

I changed aei unit to another incase this failed (had 2 go this year on other cars), still no difference. Also disconnected the knock sensor but made no difference

At this point i'm getting abit stuck with what else to check in the limited daylight time we had, I did think about poss timing issue but the owner then told me when the cars cold it seems ok only when its warmer does it do this :confused: That's when I got confused

Anyone got any ideas?
I was looking into checking cam timing and dizzy timing next, apparently its an 'all singing and dancing' engine in there but without seeing it all i'm taking what the owner has told me with a pinch of salt

[michael tierney]

i'd say carb clogged or boost enrich seized but distributor in wrong does ring a bell:)

[Markey Mark (BD)]

i'd say carb clogged or boost enrich seized

I've had carb apart and it seemed ok but its a shame I didn't have another spare as could of tried that
Might see about assembling another one to try on it

[*Yellow*]

Very similar to my last RR visit. Couldnt get mine to rev at all.

My moneys on the cam/timing.

[Andrew Cooke]

how does it idle? does it have much overlap?

Plug colours all the same? Where are you measuring boost? Dizzy out of position?

[Markey Mark (BD)]

Very similar to my last RR visit. Couldnt get mine to rev at all.

My moneys on the cam/timing.

I think that's what I was thinking of too, as its only taking the cover off I may well do that to be sure

[James5]

Incorrect cam timing

[Andrew Cooke]

Incorrect cam timing

compression test might help diagnose that, probably worth doing anyway

[Markey Mark (BD)]

how does it idle? does it have much overlap?

Plug colours all the same? Where are you measuring boost? Dizzy out of position?

It idles fine, had few little issues but thatw as only down to bit of dirt in the idle jet once I drilled it out

Plugs were all replaced by the owner so are fairly new, he done few miles driving it back now so can check them again when see it next to see if we have a nice even colour on all of them or if ones looking odd

Its measuring boost from the carb base so the engine is getting 20psi

With the dizzy that's one thing i'm looking to check next, I ran out of daylight when I saw it last which was a pain as i'd liked to of checked this before it left
I did ask him to leave car but he had no way of getting home

[Markey Mark (BD)]

compression test might help diagnose that, probably worth doing anyway

Once I get my hands on it again i'm hoping to go through all those, I was steering to timing of some description weather it be cam or ign timing

[Andrew Cooke]

do you know what the cam is, and what compression ratio it should have?

[Markey Mark (BD)]

do you know what the cam is, and what compression ratio it should have?

No this is what i'm abit suspicious about, the owner started reeling off an 'apparent' spec of the engine but I said to him without actually checking it who says what's in there. I think the only way to know what cam is in there is to either measure lift or remove it and check
As for comp, without removing the head to check head thinkness and pistons I wouldn't like to say

When he started talking 'pub talk' bhp figures its apparently done I just carried on working

[Andrew Cooke]

the other possibility is spark power, outside of the more obvious rotor arm, dizzy cap, and leads you have AEI ground and supply.

Has the engine always been like this, or is it a new problem?

[Markey Mark (BD)]

the other possibility is spark power, outside of the more obvious rotor arm, dizzy cap, and leads you have AEI ground and supply.

Has the engine always been like this, or is it a new problem?

Yeah we seem to have a good aei supply and ground, I tried a know working aei unit too to rule this out also and tried it with knock sensor connected and disconnected

From what he says when he first got it it seemed ok but has slowly got worse to the point where it lacks serious power
Weather it was there when he got the car and never really noticed I couldn't say

With the engine spec, he said it was an 'all singing and dancing' engine yet when I check it had a completely standard carb :confused: Just things like this make me think some things been changed from what he thinks in there

[Andrew Cooke]

No this is what i'm abit suspicious about, the owner started reeling off an 'apparent' spec of the engine but I said to him without actually checking it who says what's in there. I think the only way to know what cam is in there is to either measure lift or remove it and check
As for comp, without removing the head to check head thinkness and pistons I wouldn't like to say

When he started talking 'pub talk' bhp figures its apparently done I just carried on working

ahh, so checking compression will only tell part of the story....

I think this would be my plan of action:

1 - measure voltage at AEI pins with engine running, compare to battery
2 - plugs out and look at colour
3 - compression check
4 - check dizzy alignment
5 - check cam timing

This order is based on the ease of checking things rather than the relative likelihood of them being a problem. Poo-poo this at your leisure :)

[Markey Mark (BD)]

ahh, so checking compression will only tell part of the story....

I think this would be my plan of action:

1 - measure voltage at AEI pins with engine running, compare to battery
2 - plugs out and look at colour
3 - compression check
4 - check dizzy alignment
5 - check cam timing

This order is based on the ease of checking things rather than the relative likelihood of them being a problem. Poo-poo this at your leisure :)

That's ok mate, very grateful for the input ;)

I was thinking of those things to check next but as you say I think I will go over the aei unit again just to make sure, may even loop the aei relay out to eliminated as much as I can

Once I've done these checks will post my findings, never know may help someone else out in the future

[Andrew Cooke]

trying to think of quick ways to check stuff.

dizzy timing, look at the position of the burn mark on the rotor arm - shouldn't run off the edge.

cam timing, check inlet and exhaust valve lift at TDC, no need to set up a degree wheel, if it's dialled straight up they'll be much the same. If you measure total lift (combined with LATDC) you can probably have a reasonable stab at the cam spec from the wizard, although it might be better to measure pushrod lift as I don't know how accurate the rockers are.

Plug leads, measure the resistance to confirm their condition, you don't need to remove them from the dizzy cap.

Dizzy cap, I seem to recall a problem with the centre carbon electrode failing/missing :scratch:

[*Yellow*]

Once I've done these checks will post my findings, never know may help someone else out in the future

Will help me :)

On our first run on the rollers, we made half our usual power with exactly the same set up after a bottom end rebuild.

Played around with carbs, plugs etc. and still 70bhp short. So flat it was embarrassing, glad the thing went bang again!!!!!!

[andybond]

Screaming poor / bad cam timing. Even if the timing is a mile out it will still idle ok.

[Dave Reed]

I had a similar problem years ago.. Turned out one of the boost pipes had split!

It was driving me crazy for about a week! Lol.

Still made boost on the gauge too

[*Yellow*]

It idled perfect :)

[JP Racing]

Another thing ive had in the past was my pace intercooler went a bit wrong. The flap which helps the air flow through the intercooler broke off and was rattling round the inside. It slowly lost power until it became really really bad. It still made boost fine so as i was checking pipes i happened to take the intercooler off and heard it rattling round the inside. Sounds silly but things your not expecting can drive you mad looking for them so worth a look.

[SCHWARTZ]

Don't take any ones words for granted on what has been done and checked matey, do them again yourself.

[philr5t]

The 2 things I would say its down to mark is either as dave says a boost leak or a split boost pipe or hose look at what my car has been doing lately where I'm to lazy to sort the pipe out boost is set at 26 psi but as soon as the boost pipe comes loose it only runs 19psi max and feels very lazy with the lack of that aggressive feel or its the cam timing had it many years ago when someone dialled my cam 12% out it was sluggish no pull to it and it was almost like the car had no turbo fitted to it and it would only make 140ish bhp at 15-18 psi down at glen t dynatech. Got someone else to re do cam timing and the car felt totally different and felt it had found a lot more power.

Failing that i bet the turbo has had it

[rs250nut]

If you are seeing 20psi at the manifold its unlikly that it has a boost leak, compression test is needed, what are the plugs gapped at have you tried spraying carb cleaner around the inlet manifold/head?