Low RPM + High boost = Bent rods?

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Re: Low RPM + High boost = Bent rods?

Postby BennVenn » Wed Apr 07, 2021 1:07 pm

Hopefully have the TBI hat welded up today and a boost pipe bent and it'll be ready.
IMG20210405121110.jpg

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Re: Low RPM + High boost = Bent rods?

Postby 'quipt4it » Wed Apr 07, 2021 1:20 pm

Keep 'em coming...

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Re: Low RPM + High boost = Bent rods?

Postby BennVenn » Wed Apr 07, 2021 2:48 pm

IMG20210407140003.jpg

Need to grab some 120mm plate from town to finish the hat. My 38mm pipe looks far too small for the charge pipe so I'll get some 45mm stuff tomorrow (or maybe larger and squash it towards the hat end) . It's about as big as the hat will allow and will fit the turbo outlet nicely. The throttle plate also Looks to be 45mm

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Re: Low RPM + High boost = Bent rods?

Postby 'quipt4it » Wed Apr 07, 2021 4:31 pm

Nearly there!
As suggested, go carefully on boost and timing. It's not just rods that are susceptible, pistons come in for a pounding as well.
If the AF/R's are good it should be a reliable runner :turbo:

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Re: Low RPM + High boost = Bent rods?

Postby Charlescrown » Wed Apr 07, 2021 5:58 pm

Avoid pre-ignition at all cost and I am confident your engine will survive for a while anyway.

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Re: Low RPM + High boost = Bent rods?

Postby 'quipt4it » Thu Apr 08, 2021 2:43 am

Another thing to consider is engine bay heat.
That is one very cosy confine, lots going on in a small space. Have you thought about a turbo blanket and header wrap.
To remove some engine bay heat you could add louvres or just cut a hole in the bonnet and use a scoop.
Are they A/C hoses, they will need wrapping/ insulating/ shielding as well.
MPI will fare better in terms of fuel delivery and distribution, is that worth thinking about.
Also, can that injector and the fuel pump supply enough fuel. Keep an eye out for 'salt and pepper' on the spark plugs.
If you miss the knock with the sensor, that is a tell tale sign of pre-ignition.
The head gasket will likely give before any hard parts (on a stock engine), that is another limiting factor for timing and boost.

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Re: Low RPM + High boost = Bent rods?

Postby BennVenn » Thu Apr 08, 2021 7:38 am

A turbo blanket and heatwrap are planned. Yes that's the AC lines and will be about 2 inches away from the turbo when secured back to the chassis. They were originally that far from the headers in the stock config with some heatwrap so I guess they're OK with heat - within reason.

The tbi fuel system runs at 12psi. The pump used is the same for the mpi (3bar) and also same part number used in the ca18det version of the n13. I think flow should be OK. I won't change to mpi on this motor, I'll just drop the 1.8 in when the time comes.

I'm using an injector from a 2.2L motor. The 1.6 injector approaches 100% duty at wot at 6000rpm at 12.0AFR. I should be able to get away with 6psi up to 5000 on the larger injector... Maybe...

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Re: Low RPM + High boost = Bent rods?

Postby 'quipt4it » Thu Apr 08, 2021 7:48 am

That's what I like. A well thought out plan :thumbup:

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Re: Low RPM + High boost = Bent rods?

Postby BennVenn » Thu Apr 08, 2021 10:52 am

I was watching HPaccademy's VNT tuning video last night, looks like it might be a bit of a handful trying to tune this on the declo. The engines VE changes depending on the turbo's nozzle position which changes with load/boost/heat/RPM. I've never given this much thought but the same would apply when the wastegate opens on a traditional turbo setup. VE would increase but that would be more predictable as it would be only on the target boost row/column. More to think about!

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Re: Low RPM + High boost = Bent rods?

Postby 'quipt4it » Thu Apr 08, 2021 10:58 am

Can you post a link to the video.

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