EFI with big cams
 

Guys, i have aother question. I have installed a new cam. 230@ 50 with 595 lift and 114 lobe separation. Is there any problems with map senors and idling on the 454 Mag with a cam of this size. Its a 1999 engine and has the cool fuel. I have a after marker regulator and was planning on 40 pound fuel pressure to start. I have ported heads a little as well as the intake so should flow a little better than stock.

Re: EFI with big cams
 

I think the 1999 MEFI 3 engines have 43 psi fuelpressure stock. It is hard to predict to what extent your modifications alter the flow vs the MAP reading at various rpms. But a guess is that you would need to go upwards from 43.

Re: EFI with big cams
 

43 psi static reading that is. What perpormance gains do you see with the new cam versus stock?

Re: EFI with big cams
 

Donzi502 - you need to talk to a programmer.

Fuel psi is one dimensional. Programming is much more than one % change across the board - as fuel psi change would be.

Fuel psi is important and I always have an adjustable regulator set-up, but this is for fine tuning. Again, it won't tell the computer you have a different engine that has different paramters then what was originally in there.

Re: EFI with big cams
 

I believe what you are driving at is something I read on here a couple of years ago, when the 496's first came out. There were improvements made to the intake flow capabilities and the corresponding additional fuel requirements were addressed with larger fuel injectors. The fuel injection computer gives a given shot of fuel for a given load and RPM. Assuming that the additional airflow is across the board increase percentage wise, by the same percentage of additional fuel you need to increase. I further remember that 10 lb increase in fuel pressure correlates to a 7% increase in fuel delivered. You may have to consider trading your injectors for the next larger size or even two sizes larger. Realistically you need to monitor you A/F ratio with a wide band to tune it.

Re: EFI with big cams
 

Dont want to seem dumb. What is a wide band. Jas

Re: EFI with big cams
 

A wide band is an oxygen sensor that will read exact air/fuel ratio under different load/throttle settings. Most remappers like Tyler Crockett will use one on a dyno to tailor the fuel curve appropriately for the engine set up. You can also have your exhaust modified and install one on the boat to remap that way.

Re: EFI with big cams
 

Donzi- You are correct to be concerned about too big of a cam with a speed/density type system with a MAP sensor. A map sensor needs a stable vacume signal in order to have good idle characteristics. Too much duration or too small of a lobe separatation angle will cause problems.
The good news is that your cam at [email protected] and a 114 LCA should not cause a problem with that engine. I have almost the exact same cam in my modified 502 mpi's and they idle great.
You didn't mention whether you had your ECM remapped. That is important for you too see the benefits from the bigger cam. The final fuel pressure is really a function of the modified fuel map that is used when the ecm is reprogrammed. My fuel pressure is set at 48psi. My ecm was done by Jim at Arizona Speed.

Re: EFI with big cams
 

You will need bigger fuel injectors and the ECM reprogramed. If you are running the boat with the stock injectors and ECM you are most likely running lean. Lean is BAD "Boom". I have a programable ECM and O2 sensor to adjust my map. It takes many hours of tuning to dial it in.

Re: EFI with big cams
 

call Marc .... precision marine ... (504) 469-7463