question for efi engine experts
#11
Registered
Re: question for efi engine experts
Those NGK are not the best in the world even on the MSD. Cut them back to .035 and restore your initial advance on the dist. Personally I have had best results from the AC spark plugs from SBC and BBC. You wouldn't think it but they are tough, reliable and easy to read plugs.
Also you boasted about your fuel pressure but no matter what anyone tells you a fuel pressure taken at idle only tells you one thing: "That your fuel pump is running". On an EFI you MUST get a true reading at WOT being sure it holds maximum pressure with NO drop off until the throttle is pulled back. Otherwise fuel pressure readings are as useless as a screen door on a submarine.
Roby
Also you boasted about your fuel pressure but no matter what anyone tells you a fuel pressure taken at idle only tells you one thing: "That your fuel pump is running". On an EFI you MUST get a true reading at WOT being sure it holds maximum pressure with NO drop off until the throttle is pulled back. Otherwise fuel pressure readings are as useless as a screen door on a submarine.
Roby
#13
Registered
Join Date: Jun 2003
Location: Atlanta, GA
Posts: 220
Likes: 0
Received 0 Likes
on
0 Posts
Re: question for efi engine experts
As Tomcap has stated, your boat will see the best speed with a 3blade, ( deep V with conservative X setting) which is why you lost speed with the 4blade...
With the engine...my best guess is the exhaust you chose doesn't flow enough to take advantage of the ecm reprogram which has resulted in a rich condition and thus loss of power and response. Only a few aftermarket exhausts actually require a reprogram of the ecm because they put the 502EFI into a lean condition...most will not and work best if the ecm is left alone. The only headers that I know of that require ecm reprograms are basically tubular headers, such as CMI, Lightning, Stellings, Eickert.
With the engine...my best guess is the exhaust you chose doesn't flow enough to take advantage of the ecm reprogram which has resulted in a rich condition and thus loss of power and response. Only a few aftermarket exhausts actually require a reprogram of the ecm because they put the 502EFI into a lean condition...most will not and work best if the ecm is left alone. The only headers that I know of that require ecm reprograms are basically tubular headers, such as CMI, Lightning, Stellings, Eickert.
#14
Registered
Join Date: Jun 2003
Location: Atlanta, GA
Posts: 220
Likes: 0
Received 0 Likes
on
0 Posts
Re: question for efi engine experts
One more thing...its not your plugs..and NGK are the best in the world and what I run in all my cars and boat with no problems.
My engine? HP500 built by Innovation Marine. Plugs they install in this and thier HP525 and HP600? NGK V-power #7's. Gap at .045.
The ecm reprogram will or should have a more aggressive spark advance in it.
My engine? HP500 built by Innovation Marine. Plugs they install in this and thier HP525 and HP600? NGK V-power #7's. Gap at .045.
The ecm reprogram will or should have a more aggressive spark advance in it.
#15
Registered
Re: question for efi engine experts
Originally Posted by 26sonic
robyw1 what part no. do you recommend for the ac plugs ? thanks for the info !
Roby
Last edited by robyw1; 06-17-2004 at 08:34 PM.
#16
Registered
Join Date: Jun 2003
Location: Atlanta, GA
Posts: 220
Likes: 0
Received 0 Likes
on
0 Posts
Re: question for efi engine experts
The AC plug of choice is MR43TS..or if you don't boat in salt water you can use the auto version, R43TS. This is the extended tip version of the R43T plug and gives you a smoother idle and better resistance to fouling and recommended by Dennis Moore in his Marine Bigblock and Smallblock GM performance books.
PS. Same plug used for small block GM's.
PS. Same plug used for small block GM's.