ECM is off a 99 C5 corvette. I believe these are the EH-528 Ecu’s? I was just wondering how these ECU’s would act if introduced to small amounts of boost using an FMU for enrichment. What does an untouched LS PCM do if it sees boost? Will it just max out the MAP/MAF quickly? Or will it throw codes and cause problems. I’ve never worked with an OEM ECU.

A friend came across an old procharger kit for a 98 c5 corvette. (he thinks it’s a procharger kit anyway) Considering installing it on a 1999 C5. The kit comes with an FMU for fuel enrichment though. I’ve used FMU’s in the past with great success on VERY mild boosted setups. (4-6 psi). But I’ve never seen them used on an LS platform. Looking online I see no kits that came with any sort of FMU for a corvette. So I’m guessing this may not be part of any original kit.

I know HP tuners or some sort of aftermarket ECU would be best. What I’m wanting to know is if an FMU can be made to work with a 99 LS PCM. And If so, what must be done.

 

The pcm will have to be tuned to run a procharger, on a vette there is a 99% chance it will go into reduced power if you tried it untuned.

 

Do you know what would trigger the fault? I know on the map sensor cars we would use a one-way “vented” check valve going to the map sensors to prevent vent any pressure it may see. Would that possibly work without throwing a code? Or would the MAF reading be the issue? What happens if the MAF is maxed out on the GM ecu? Do they throw codes? Or just stop providing additional enrichment?

Thank you!

 

usually it pins the maf vs lbs min overflow table

 

If you tried it with a stock tune it would exceed the values in the ETC predicted airflow table which would throw a P1514 dtc and make it go into reduced engine power.
As soon as you hit any boost it will ped out the stock map sensor, that isnt a big deal. On low boost you will not max out the maf but it would cause issues with the maf/map table if you dont adjust the tune. If you max out the maf table it will go into reduced power in a C5.

There is no way around getting the pcm tuned if your wanted to add any kind of boost or to a c5. If you going to to do any mods past basic bolt ons it will have to be tuned.

 

Thats what I needed to know, thanks...