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Loss Of Power under Hi Boost

Robo's

By Robo's,
in Engines & Forced Induction

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Robo's Mentor

Robo's

Posted
Posted

Ive upped the ante on the 2530, raising it too 17psi, and now i get a sudden total loss of power in the mid range. As i accelerate hard in 3rd from 3000rpm, i get 1 or 2 sudden losses in power for a split second and then it comes back, its between 4000-5000rpm. Im thinking its the standard AFM to Turbo rubber pipe being sucked in fully and then re-opening under hi boost.

Opinions?

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Robo's Mentor

Robo's

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Posted
I heard SAFC-II does not correct/modify your ignition timing and so that may be the cause??

Your right it doesnt alter ignition timing, but still doesnt explain total power loss. Im not meaning a slight surge, i mean no power.

I think its the AFM

If i reduce the boost by 1psi, it doesnt do it

paulr33 Grand Master

paulr33

Posted
Posted

17psi and stock ecu cant be good, it will just cut the timing and limit stuff

get a remap, check for sale section, $350 swap in swap out, rev limit change, boost remove and speed cut remove, change of timing, ignition and other stuff you may need

Cubes Grand Master

Cubes

Posted
Posted
Your right it doesnt alter ignition timing, but still doesnt explain total power loss. Im not meaning a slight surge, i mean no power.

I think its the AFM

If i reduce the boost by 1psi, it doesnt do it

I tried to run the RB30DET on the stock RB20T ecu, the fuel cut was hitting with the AFM reaching 60% at 2000-2500rpm & about 8psi of boost.

The AFM wasn't maxing out, but the injectors appeard to be, just before the fuel cut the afr's would go dangerously lean in to the 14:1 AFR.

The ECU was freaking out because the fuel requirements were out of its map (I assume) Either that or the injectors were at 100% duty cycle which is possible as the RB30DET makes more power on 6psi than the rb20det did at the same rev's etc at 11psi due to the much larger valves & ports.

The ECU has to try to raise the duty cycle to get the required fuel in, not as much fuel pressure is being run due to less boost being required to make the same power.

This would also apply to running a larger turbo because the airflow is greater at any given boost pressure compared to the stocker.

If the new turbo makes 200hp at 5psi and the old one made 150hp at 5psi then you will be lacking fuel pressure for that extra 50hp as for the old stock turbo to make 200hp it may need say 8psi which will increase the fuel pressure via the rising rate regulator for that extra 50hp. Hence the injectors don't need to run as much duty cycle.

The base maps are designed around the rising rate fuel pressure regulator & stock turbo (airflow per psi) etc.

As soon as you throw out this airflow per psi and make the car much more efficient be it cams or bigger turbo it will throw things out quite bad as I found out.

lol If that makes sense.

I had the SAFC adjusted to max everything, as much fuel as it could pump in and the AFR's still would not pull in line. It only made the fuel cut hit much much earlier.

It seems to be related to the amount of air the car is sucking (nothing to do with boost) at that particular RPM. The ECU thinks some thing is wrong and first begins to play with the ignition timing (mine dropped from 22degree's to 8 degree with a big power dip at ~6psi) then it fuel cuts if you start sucking even more air (by ~8-9psi).

EVEN if the AFM hasn't maxed out yet.

lazza Enthusiast

lazza

Posted
Posted

Get it on a dyno (if you havent already), to check the fueling. It could be the spark plugs, what gap are you running? At that boost it could be that the spark is being blown out, although that would occur more at high rpm? Try plugs one colder than standard and with a maximum of 0.8 gap.

I would say if the ECU hasnt been remapped it will need to be to run 17psi on a bigger turbo.

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