Boost

[hsv300]

Hi guys a quick question: If i increase boost on a supercharged motor from 8psi to 16psi do i have to retune the motor or will the Autronic pickup the extra pressure and do its magic?

Cheers Greg

[MRMRacing]

IT depends on how your base fuel table look, normally they will do that automatically if it is tuned in a proper way.

[Ian]

If the ECU is configured for MAP or MAP/TPS fuel tuning then the ECU will see the change in boost. But I have seen some tuners configure supercharged engines by TPS only and this configuration will not see the change in boost and will absolutely need to be retuned.

If configured for MAP or MAP/TPS and depending on how the fuel table is configured the fuel will probably be compensated in a safe way. But the ignition table may not be correctly configured. You should check the calibration carefully before changing the boost.

But are you sure the engine is capable of the extra boost? From your username I guess you have a v8 which might already have a reasonably high static compression ratio for a boosted application. Going from 8 lb to 16lb is theoretically about 35% increase in cylinder pressure.

[hsv300]

Thanks Ian/Robert I am running a 4.6l Ford SVT Terminator motor from States which came with a stock supercharger on the 2004 Mustangs it has forged crank, H-beam forged rods ect and running Compression ratio of 8.5:1. I will recheck the cal file but i think its set to BARO/MAP ?

Cheers Greg

[underpsi68]

I would check/retune if needed. The blowers efficency/inefficency will play a big part in the tune. Is this a stock blower? If so it is not that efficent in that psi range.

[hsv300]

I would check/retune if needed. The blowers efficency/inefficency will play a big part in the tune. Is this a stock blower? If so it is not that efficent in that psi range.

This is correct at the moment its around 8psi with the pulley change it would only be around 12-14psi which is still on the limits of the Eaton 112. If i upload my cal file can someone have a look over it?:)

Greg

[hsv300]

Just checked over the tune I had done earlier this year to see about increasing the boost and noticed hey have changed the compression ratio from 8.5 to 9.8!!! Can I just change it back to 8.5 or do I have to get a new tune again.

Cheers Greg

[Chris]

What is the reason for this change?

Chris

[hsv300]

No idea let's start from the beginning I have built a AC Cobra replicate here in Australia imported a SVT cobra 4.6l Terminator motor with the factory supercharger from the USA.

Got the Autronic because other cobra owners here are using this ECU and i could get a startup cal file. The original file had the comp set at 8.5 which is correct for this motor when I check the tuned cal file from the company that tuned it they have changed it to 9.8 I have no idea why they did this I will try and ring them in the morning and ask, but it should be set to 8.5 correct?

Greg

[Ian]

It seems that the tuner maybe loaded their own cal before tuning (possibly from another tune on a similar combination) and didn't realise that parameter was different.

If it has been tuned with that value (and it seems like it has) then don't change it because the CR parameter is included in fuel delivery calculations. If an incorrect value is used in an engine tune some of the Base Fuel Delivery table numbers will have been tuned around it but the engine will run correctly.

If however you are going to have the engine tuned for another reason then fix the CR parameter before the tuning starts.

[hsv300]

Thanks Ian I think I will get another tune done with correct CR parameter and the extra boost.

Thanks for your prompt reply.