My draw through turbo

[advinnie]

Four truck coils that sounds interesting what ignition system are you running? Any photos

[advinnie]

Hi all I need so advice from you turbo god's. I know I've figured something out but I'm not sure what it is?
Sorry but this may turn into a long post.
Where to start, right I was running a max constant boost of 11 psi BUT my ignition timing was retarded all the way back to 15 degrees BTDC (I would get detonation @ 17 BTDC)
AT 8psi boost I was down to 22 degrees BTDC to stop detonation. Anyway I did a full rejet of the carbs and decided to start the process of timing from the beginning so fitted the 5psi wastegate spring to limit my boost untill I got the low boost timing sorted.
Now @ WOT and at 101Kpa ( no boost ) my max timing is at 32 degrees BTDC @3200 rpm, now at 5psi I can run 29 degrees BTDC at 3200 rpm with no detonation at all and the torque is amazing BUT this is what I've figured out. Now at 8psi like I said I'm at 22 degrees BTDC but the engine torque doesn't feel any stronger than when I was at 5psi and the strange thing is when at 11 psi I have to drop the timing to 15 BTDC to stay clear of detonation and once again at this boost level and ignition timing the engine torque feels even weaker than when I'm running 8psi. All so doing some timed runs the car is faster when on a constant boost of only 5psi when compared to when I'm running 11 psi.
Now here's my thoughts,
Is this happening because at 11 psi boost the timing is so retarded to stay clear of detonation that I've moved to far away from best torque timing and mostvof the combustion energy is leaving through the exhaust valve ? (if that makes sense?)
I hope you understand what I'm saying if not let me know and I will try and explain it another way.
I've even tried making the A/F mix mega rich @ 10.2:1 but that's made no difference

[66brm]

How are your valve springs?, you may be finding their limits

[advinnie]

Valve springs are the signal HD ones and have been on this engine for two years now ( around 2500 miles)
What exactly do you mine by they may have reached there limit?

[madmike]

as in ''Floating the valves' this is when they are bouncing off the seats
valve springs need to be replaced every now & then I figure there consumables

[advinnie]

I see. When I first started this two years ago I was using stock springs and I would get valve bounce at all different boost levels and rpm's and when it happened the engine would go quite and loose 90% of its power briefly when it was happening, this is not what's happening now. Now I'm getting a sound like something is loose and bouncing along the ground and rattling but there is no drop off of power when this happens but if I retard timing of go mega rich with the fuel the sound goes but because I have to go very retarded with the timing to run higher boost I'm loosing torque.
So the question is do I just run lower boost of 5 psi and only drop the timing a degree or two witch the engine I must say feels great or run 8 psi and a retard timing of only 22 degrees BTDC witch is the max boost I can run without loosing torque, YES I can run 11 psi I've even ran 14psi but the timing gets do retarded there is no gain in power, all I get at this point is a good story to tell down the pub cause all that matters in pub talk is boost figures and saying " I'm running 14 psi boost" is a lot more impressive than saying " I'm running 5 psi boost" although there's more power at the 5 psi boost setting but down the pub no one cares about that .
Also he's something else I be found out, at 5 psi boost and 28 degrees timing the exhaust temperature feels normal, at 8 psi and 22 degrees BTDC the exhaust feels a lot hotter AND when running 11 psi and higher with a timing of 15 degrees BTDC the exhaust manifold is starting to glow.
So here's my conclusion.
Any timing retard after 22 degrees BTDC is to late and is heating the exhaust system and exhaust valves up to much. So the retard timing limit of 22 degrees BTDC is also limited the boost level to 8 psi boost max.
Now the last bit of information is that when running 5 psi boost @28 degrees the spark plugs stay clean, sat 8 psi and 22 degrees BTDC the plugs seem to foul up within a few hundred miles and when running 11 plus psi and a timing of 15 BTDC the spark plugs are fouling up very very fast like with 50 miles or so and I'm not to sure why that is as of yet?

[Chip Birks]

Sounds like you need to get on a dyno. I have the same problem, i have a seat of the pants expectation, but, it doesn't tell the whole story.

[advinnie]

Yes I know I do need to get this thing on the Dyno to see what's going on.
All I can say is that by doing some timing runs and and using my own body as an instrument it most definitely feels that max power/torque is at 5/6psi of boost plus I only have to retard by 3 degrees at this point, from this point if I increase boost to gain more power I get detonation so I have to retard timing hard and fast to stop it but at the same time doing this I loose power. So my torque curve seems to level off at what ever torque I'm getting at 5 ish psi ( this is why I need the Dyno to tell me what the engine is putting out at this point) plus the move I retard the hit the exhaust gets but I have no temperature gauge to measure it. This morning I did a few more runs and still need to set down and work out the data but I wanted to see what timing I had to have to reach 14psi and the answer to that is 10 degrees BTDC @3200 rpm. That's a drop of 22 degrees in only 14 psi that's almost double the basic rule of thumb of 1 degree per psi

[madmike]

stick to lower boost levels and stay out of them 'Pub's' or start lying just kidding

[advinnie]

Staying out the pubs is a no go so I guess I need to get better at lying
Im going to get my home made water/methanol system back up and running and see if that helps at all.

[gbaker770]

You should not have to back that much timing out.
I ran 14 psi at 9-1 with timing locked at 24 degrees on pump gas. We ran it up to 26 psi with the same timing on C-16.
I’d start by getting some way to figure out what your afr’s are.

[advinnie]

You should not have to back that much timing out.
I ran 14 psi at 9-1 with timing locked at 24 degrees on pump gas. We ran it up to 26 psi with the same timing on C-16.
I’d start by getting some way to figure out what your afr’s are.

Are you runners Ng draw through or blow through?
And carb or EFI if carb what jetting ?

[advinnie]

I will have to connect my innovate lm-2 back up but at the moment of the top of my head I'm running a 1.34 main with a 24mm vent and a 1.45 main on the other barrow with a 28mm vent and at 5psi boost I was getting a A/F ratio of 11.3:1.
I will up the mains a little more and see what I get.
Anyone else running a Weber draw through if so what boost you running and what size mains

[Maddward]

I'm running a 40 DCOE draw through with 30 vents on both barrels, 1.40 mains on both. 7 psi at the moment. AFR is 11.5-11.8 at WOT and I limited my 009. Timing is 12 deg at idle and 24 maxed out. Hope this helps!

[advinnie]

I'm running a 40 DCOE draw through with 30 vents on both barrels, 1.40 mains on both. 7 psi at the moment. AFR is 11.5-11.8 at WOT and I limited my 009. Timing is 12 deg at idle and 24 maxed out. Hope this helps!

Thanks mate