Alpine R8 GT Turbo Too?

[BobG]

We have boost!

I disassembled the turbo and couldn't find anything amiss. After reassembly the flow from the oil drain was much better and no oil leaks. I did a quick accel run and the car had much more power. The realtime MAP readout was about 140 Kpa so 6-8psi. The waste gate is set to 7psi. The dump popped during decel. And nothing exploded... except the fan somehow contacted the radiator and caused a leak. I'll have to get it repaired before I can do more testing. I can't wait!

Thanks all for your suggestions and patience.

 

[Steve Swan]

Well that's sorta good....

 

[Adey]

a step in the right direction for sure

 

[DaveL485]

How strange! I wonder what the issue was.

 

[BobG]

I got the radiator repaired and back in the car. The damage occured when the radiator bulkhead flexed and the rad hit the fan. I didn't have the bulkhead fully bolted in (DOH!)

Did a couple of acceleration runs yesterday just before it started snowing. Full throttle in 1st and 2ng gear on a flat parking lot. The boost was very noticable with my butt dyno! The data log showed a max MAP sensor reading of about 130 KPa, so 30 KPa above atmospheric or about 4 psi boost at 5000 rpm. My wastegate actuator is set at 7psi, so I assume is wasn't opening. Pardon my ignorance of things turbo, but should I expect to hit 7psi (or higher) with more load, say on an uphill run, or in a higher gear?

Now I'm trying to figure out how to log AFR sensor data with my MicroSquirt ecu.

 

[Brigsy]

Id hazard a guess that the boost is only 4psi due to pressure drop.

 

[BobG]

I Did some more road test runs yesterday. Here's a sample datalog from a short uphill run in 2nd & 3rd gear.



Plots are RPM, MAP, AFR and KNOCK. Max boost was about 6psi at 5460 rpm. The wastegate actuator is set at 7 psi. I'm wondering if it's starting to open. I'll disconnect the hose to the wastegate actuator for my next run and see what happens.

Also the AFR drops to about 10 as boost increases. Is this supposed to happen? Is the low AFR reducing power (and boost)? The AFR during cruise is 13-14 so that's good.

All comments/suggestions are welcome.

 

[andybond]

Also the AFR drops to about 10 as boost increases. Is this supposed to happen?

Sustained , or drops and recovers to around 11.7 - 12.3?

Is the low AFR reducing power (and boost)?

Power , yes. It will suck the life out of the car and if at 10ish the EGT will be low but its very very rich.

You can start to advance the timing and fuel trim to suit.

 

[BobG]

Sustained , or drops and recovers to around 11.7 - 12.3?


Power , yes. It will suck the life out of the car and if at 10ish the EGT will be low but its very very rich.

You can start to advance the timing and fuel trim to suit.

AFR recovered to about 11-12, then to 13 while accelerating in 3rd gear then drops to 10.7 at peak rpm in 3rd.

I haven't started advancing timing yet. Don't have my knock detection setup calibrated.

 

[andybond]

AFR recovered to about 11-12, then to 13 while accelerating in 3rd gear then drops to 10.7 at peak rpm in 3rd.

I haven't started advancing timing yet. Don't have my knock detection setup calibrated.

It sounds about right , but hard to tell without seeing a log. I personally think in isolation 10.7 at WOT is too rich. It will for sure be sapping some power.

 

[BobG]

I posted the log graph. It shows up on my computer. Hmm ....

 

[andybond]

I posted the log graph. It shows up on my computer. Hmm ....

You did , but its hard to analyse. Live log is better or at least on screen so can trace back and forwards easier.

It needs cleaning up a bit so something like :

 

[BobG]

Can I attach a log file? Or can I post a live log?

I have smoothing turned on (average of 5 points). Should I average more points or is there a better way to smooth the curve?

Thanks @andybond. I'm new to all this datalogging stuff!

 

[Brigsy]

10s a bit rich. Aim for 11.8-12.0 @WOT/full boost.

I wouldnt personally take actuator pipe off as it will probably send it to the moon and boom if your not careful. Add more preload to actuator or bleed off the actuator line.

Id run a half decent pre calibrated knock headset or similar whilst tuning and set your knock sensor up later. I dont run one on mine as pics up loads of false noise, or nothing at all.

 

[andybond]

set your knock sensor up later. I dont run one on mine as pics up loads of false noise, or nothing at all.

Lotus removed these from their race series as picked up shed loads of noise.

 

[BobG]

I wouldnt personally take actuator pipe off as it will probably send it to the moon and boom if your not careful. Add more preload to actuator or bleed off the actuator line.

I checked the wastegate actuator and there was about 1mm preload. It should be 3mm for a 6psi opening. I reset the preload to 10mm which should give 7psi. Thanks for the advice Brigsy.

10s a bit rich. Aim for 11.8-12.0 @WOT/full boost.

A couple more runs today. Boost was over 7psi with actuator reset. But AFR was still near ten.

Ideas on how to increase the AFR at high boost? More advance? smaller carb jets?

 

[andybond]

increase the AFR at high boost? More advance? smaller carb jets?

In normal circumstances there is no relationship between advance and AFR. Something would normally have to be right out of kilter for that to happen.

You could listen for knock/det with some cans and increase the boost. That will use up some of the "spare" fuel , or change the jets as you mentioned. Be careful mind!

 

[BobG]

In normal circumstances there is no relationship between advance and AFR. Something would normally have to be right out of kilter for that to happen.

You could listen for knock/det with some cans and increase the boost. That will use up some of the "spare" fuel , or change the jets as you mentioned. Be careful mind!

Thanks Andy. I'll take it slow.

 

[BobG]

Carb Jets:
I partially dismantled the carb to measure the jet sizes. The motor has an AFR at cruise of about 13. The wastegate actuator is set a 7psi and I'm measuring 6-7 on the MAP. However, the AFR goes below 10 at full throttle/boost.

Here are the jet sizes:
main - 120
air corrector - 90, originally 100 but filled and re-drilled
enrichment jet ( not sure if it's primary or secondary, see the photo) - 100, originally 125 but filled and re-drilled
I couldn't find the second (or first) enrichment jet

How can I lean out full boost mixture? Air corrector re-drilled back to original 100 or ever larger?
What about enrichment jets?

 

[sparkie]

First question, is your venturi still 25mm. Don't go off what is printed on it.
If it is the following is the OE spec.
25mm venturi, 125 air corrector, 120 main, 100 1st stage ( in your pic), 100 2nd stage ( the 5 Oclock hole from your 1st stage, look where it sits on the main body, there's a bush. That's the 2nd stage).
That set up is good for 14psi usually on a 1397cc engine.