type 4 turbo pinging under boost

[Garrick Clark]

Hi Guys.

I'm trying to solve a running issue on my motor.
Engine is  1911 TYPE 4.
Spec is
66x96
86a cam
42x36 valve.
lots of port work.
Kidney shape chambers
034 dizzy. petronix 3. dual vac can.
2" Su carb in front of turbo,  draw through set up
water/meth, single water injector (after the turbo)
7.5.1 comp.
41 mm internal header pipes.
B8ES plugs set at 20 thou gap.
single stainless quiet pack
10psi boost.
shell optimax fuel.
AFR is 12-13 at 10 psi at 2/3 throttle.
Turbo is  GT25 off a JCB.
No carbon seal yet.

I Think the issue is ignition timing related.
At 24* total it back fires.
If I advance it past 24* it pings.
So its either pinging or backfiring
The more I reduce the total timing the bigger the back fire.
I have tried boost retard using the dual vac can. Results in back firing.
At present its 14* -28* total.
On a turbo motor should  the advance come in quick or slow.

So what can be the fix for this.

Is there anyone in my area.(Lancashire) that has a rolling road that knows how to advice and tune an old school  draw through turbo. (No ECU or Injection).
Apart from the above issue it is pretty quick, almost OMG.

[mr horsepower]

Check your sparkplugs and do a leaktest
Is A/F correct if there is no seal in the turbo?
Or way to lean or leaking valve i would say..
Good luck

Gr henri

[mikko k]

Camshaft for N/A engine? Wrong lobe center?
Wrong kind of intake manifold after turbo? Meaning that other side of engine goes lean and the other one is rich. Picture from engine?

[Garrick Clark]

Thanks for the reply's guys.
I have checked the 4 plugs and they are all a dark charcoal colour. none are white.
I will do a leak down test soon.
AFR seems good will check it again.

I have dual springs on the inlets and singles on the exhaust, is this a  problem.

The Cam is an n/a cam for sure. So could the overlap be the problem too.
Turbo is going to be converted to carbon seal this coming week.

[Garrick Clark]

So the web 86a opens the intake at 18* btdc and closes at 18* atdc

The turbo specific cam from Web called the 119 opens the intake at 12* btdc and closes at 12* atdc

Is this a big difference compared to what I'm using.

Thanks.

[Garrick Clark]

could I ask, can some one have a look on web cams web site and compare the type 4 86a cam and the 119 cam. I don't really want to change the cam.

[Erlend / bug66]

Is the spark steady, or does it wander about?

I've seen a whole lot of ignition systems wander many degrees because of tolerances.

[mikko k]

I have dual springs on the inlets and singles on the exhaust, is this a  problem.

It's not a problem if you have enought valve seat pressure. Do you know how much?

The Cam is an n/a cam for sure. So could the overlap be the problem too.

Maybe or maybe not. 86a is a large cam for N/A engine. Turbo cams are different. Many times they have bigger lobe centers.

[mikko k]

So the web 86a opens the intake at 18* btdc and closes at 18* atdc

The turbo specific cam from Web called the 119 opens the intake at 12* btdc and closes at 12* atdc

Is this a big difference compared to what I'm using.

Thanks.

86a intake opens 18 dec BTDC and closes 54 ABDC. At 119 intake opens 12 BTDC and closes 48 ABDC. So, there is difference (advertised duration 290 versus 276), but how much is the effect, I cannot say. Also, the shape of lobes can differ. Are you sure that you have made the cam timing right?

I'm not any kind of guru, but I have once played with sidecraft weber in front of turbo. There were intake manifold problem. The center section were Y-shaped and it run badly, burnt plugs, etc. I did made a new T-shaped center and problems were gone..

[Garrick Clark]

Hi Mikko.
My manifold is a T pipe.
The T is right on the turbo out pipe, so the air pressure splits left and right off the inner wall of the pipe. The meth nozzle is positioned in the middle of the T also
to get a good separation. Hopefully. Like I say ALL plugs are the same colour.

I did put some stops on the inside of the dizzy plate  because of timing scatter. Before I put the stoppers on the timing was all over the place due to the advance   weights dancing around near the max movement of the weights.

This 034 has a soft spring to let it advance to 18* then the stiffer spring take up ITS free play and lets it go to 24*.
Can I get rid of the slack in the second spring so that I have max advance at a higher RPM. maybe then i'll get to WOT without pinging.

Thanks G.

[fish]

Try it with a locked out dizzy

[Garrick Clark]

Will do.

[Baz54]

Hi,what I have found its usually if you don't have enough cold air to fuel mixture or the Ron rating is to low. 98 is low for an engine on high boost you need 101 or higher. Try a bottle of Millers CVL it's really good stuff.

[Garrick Clark]

 Hi Baz.
I'm using shell optimax fuel with no extra additives .
I've got water/meth too. I may need to spray more water in it.
The air filter isn't really in a cold air supply ,so I could move it.
On a run the cold side of the turbo is cool to the touch
and the manifolds also are cool.
The S.U carb is very cold to the touch
I will get some of the Millers cvl you mention.
I must be doing something right with the tuning as the new clutch pressure plate isn't holding any more 

[andy198712]

Is that not a AFR you want at wot NA, so at 10psi 13afr is lean no?
What compression ratio?

Sounds like your getting there!

[Garrick Clark]

Hi Andy, Yeah its getting there now, comp is at 7.5.
Yes I think its lean as well, I thought the water/ meth would lower the numbers down.
Cant test it again just yet as I think the turbo needs an oil inlet restrictor. i'm getting a bit of oil in the manifold and a bit on the exhaust wheel.. The inlet hole on the turbo is about 3mm and the oil supply pipe is bigger. SO the turbo's getting 60 psi gushing round the bearings when cold, The out pipe needs to be better also. The oil in the fuel might be lowering the AFR Too.

[spanners]

garrick, i see you run .020" plug gap,  try the plugs at stockish gap, around .030", narrow gaps always give me trouble ive found, foul easy.

[Garrick Clark]

Hi guys. I've not done much lately in terms of tuning. I'm currently repositioning the turbo. Its going about 10 inch higher. this will make the turbo out pipe point down a bit, before it was angled upwards. (not good from what I've been reading), also the oil out pipe will be in a better position.

I'm using a Petronix 3 module. It says it has multi spark and adaptive dwell . I've been reading bad reports on these modules. Anyone using 1 at the minute with a turbo. I'm thinking this multi spark thing might have something to do with these massive bangs out the exhaust. I've had this problem ever since I went turbo. ( blow through and draw through) The petronix 3 was fitted before the first turbo test run.