why am i adding lots of fuel in the top end?

[3.0 GT]

im running the maft pro in speed density with 550cc injectors on my built 7m. new stock pump but stock fpr. turbo is holset he351. anyways from about 4300rpm if i dont add lots of fuel with the maft it runs lean. i am adding about 20-25 percent from 4300rpm to redline and during a 3rd gear WOT pull everything looks good. but when i try to do a first gear pull it nails fuel cut when i get to this area. and i am only running 11psi. any help would be appreciated:icon_bigg

 

[mhopemk3]

Did you bypass the Jtube? I would get rid of the stock FPR and get a rising rate FPR. I am running a T64 @ 18psi and I still pull fuel with the Maft Pro.

 

[3.0 GT]

yeah j tube is bypassed, but i thought the stock fpr was rising rate??? i do agree i need to upgrade tho.

 

[radiod]

Stock is a rising rate regulator, otherwise the vac line would be kind of unnecessary .

 

[3.0 GT]

Stock is a rising rate regulator, otherwise the vac line would be kind of unnecessary .

good point lol. ill try and test it somehow to see if it is actually functioning properly.

 

[mhopemk3]

You can use the stock but I would think you would be really rich at idle. Post your mods! What brand of injectors? What is the condition of them? Are they new, been flow tested? Upgraded throttle body? Are you using a wideband? Post your M-Pro settings.

 

[kneedragger85]

Did you bypass the Jtube? I would get rid of the stock FPR and get a rising rate FPR. I am running a T64 @ 18psi and I still pull fuel with the Maft Pro.

You should be pretty close to 500rwhp on 550's and 18psi with your 63mm and you're still pulling fuel? What's your fuel pressure at idle? I was looking to ditch my 550's for 680's and run bigger feed/drain lines with another Walbro to be safe with my SP63.

 

[mhopemk3]

You should be pretty close to 500rwhp on 550's and 18psi with your 63mm and you're still pulling fuel? What's your fuel pressure at idle? I was looking to ditch my 550's for 680's and run bigger feed/drain lines with another Walbro to be safe with my SP63.

I wish! I think I'm over the 400whp on pump. 18psi is a drop in the bucket for this T64. I ran 13.1 @ 113mph with a 2.5 60ft. Those times are in line with what I have seen with other lower 400whp MK3's.

My plan is to dyno as it sits and then tune for 25psi on race gas. I would agree that I may see the fuel run out at those settings. I think 680's are the right mark.

I think the FP at idle is 32-34psi.

 

[3.0 GT]

You can use the stock but I would think you would be really rich at idle. Post your mods! What brand of injectors? What is the condition of them? Are they new, been flow tested? Upgraded throttle body? Are you using a wideband? Post your M-Pro settings.

mods are built engine, 255lph pump, 3 inch exhaust, maft pro running speed density, intercooler and hardpipes, 550 injectors, intake. ill post up the maft settings later. injectors are from a rx7 but they were flow tested a while ago and all came out fairly close to each other.

 

[IJ.]

Boost referenced NOT rising rate......

What's your fuel pressure during a pull?

 

[3.0 GT]

Boost referenced NOT rising rate......

What's your fuel pressure during a pull?

thanks for clearing that up. i have no idea about the pressure because i dont have a gauge and im on the stock fpr. is there a chance the fpr is not refrencing boost? i took off the vac line and put an air compressor up to the fpr vac port and i did not notice any change on the wideband. should it go rich if i apply lots of pressure to the fpr?

 

[IJ.]

My "guess" is the pump is laying down on the top end.

Check the line from the manifold to the Fpr from memory it goes through a VSV that may have failed.

 

[3.0 GT]

damn new pump? i checked the vac line to the fpr and it is cleared and pulling vacuum.

 

[IJ.]

Put a gauge on it and see what it's doing under load....

 

[3.0 GT]

ok will do.

 

[3.0 GT]

well a little update. i put the voltmeter of the fuel pump wires and i was geetting about 11.5 volts with the car running. this is with the resistor bypassed. so i rewired the fuel pump to the battery and a relay and all that junk and now i have about 13.8 volts at the pump with the car running. so i went for a test drive. before the rewire i was getting a close to steady 11.5 afr through a wot pull. but now with the rewired pump i am getting around 10.0-10.2 afrs!!! the pump is an autozone brand replacement so idk if it is running out of flow or not. so should i raplace the fpr or the pump?

 

[hvyman]

A stock replacement pump?

Get a walbro or better yet a mk4 pump and a afpr and fine tune it better.

 

[3.0 GT]

well i only have money for either the afpr setup or a pump but i guess i could get the afpr and monitor the pressures and get the pump later and ill keep the boost down until then.

 

[hvyman]

Stock pump is maxed out at something like 330hp from what i have read. I dont know the exact amount but your running out of fuel for 400hp.

I would either spend the money on the pump so you dont run lean or drive slow and save.

 

[3.0 GT]

yeah i guess i need a new pump. i just bought a fpr setup so ill just take it easy until i can afford a pump. ill let u guys know what happens when i get the pump in. thanks for the help!