General Supercharger Thread

Question of the day, in this instance on 750 injectors. Stock FFV FPR is rated at 43psi low speed and 55-60 psi high side non boost referenced from what I've read. With that said do you guys tune your injector offset vs volts to the idle pressure of 43 psi or the high side of 55-60 psi? Looks like @43.5 psi CC/min is 725cc whilst at 58 psi CC/min is 802cc.

 

I'm set at 43psi and you can adjust PE for the increase of fuel pressure. At least that is how my @snivilous tune is set.

 

@Mdl you're non FFV correct?

 

Yes, I'm non-FFV. I also have to compensate PE for water/meth and the boost reference. Hopefully others will chime in for further clarification.

 

I don't follow how the FFV stuff works, but I would start with the injector offset at the base pressure since that's mostly where the truck will operate. In my mind the idling and low speed fueling being accurate would be more important because the high load stuff is when PE comes in and there's so much extra fueling that the offset becomes less of an issue. At high duty cycle the offset time error is pretty small compared to the overall injector open time, so the error would be less noticeable compared to low load where the injectors aren't open very long so the timing of when to command them open is more critical.

 

Ah gotcha. I only ask because I was having trouble with the 43 psi charting for offset vs volts. I cranked the values to the 58psi charting and now have loads of fuel with boost referenced. Running great at idle/partial and WOT, tapping on 9.2 max of 10.2 A/F....... New problem now is I'm maxing out Injector duty cycle....

 

If the engine is running fine everywhere and fuel trims and AFR look good, then I would run whatever configuration provides that best. If it's 58psi settings then run that.

 

Understood I started with the base of 43psi charting. Once I jumped to boost reference and WOT PE tuning I was always running lean on top now matter how much fuel I throwing at it.

 

There's a pretty good thread on HPTuners forum about disabling low pressure "mode" and forcing the fuel pump to run at 58 PSI all the time. I'd be tempted to do that and eliminate a variable.

 

She's running like a banshee at 58psi charting, I'm now concerned about injector duty cycle. Trims are great, knock is non existent, PE is rich....... But these InjDC values are insane...... And I haven't even touched timing for more power lol

 

Could lean it out a hair so the duty cycle maxes out a bit higher. Impressive it's using that much fuel with 800cc, though not entirely surprised since I've seen 95% with the 1900 blower at ~10psi without boost reference and you're probably pumping more air.

 

Yes sir I am currently fine tuning PE a wee bit leaner. But God damn I'm out of injector on prospeeds 750s already. Granted this is on the 76mm pulley where up high the muthfucka just screams..... It scares people

 

While in the realm of possibility for sure, something feels wrong to me. No one with comparable setups is maxing out 750s (well 800 in your case). @Wynnded isn't that much higher elevation and running the 70mm. @helidave just put on the 76mm and is running 535cc I thought at like 7000-8000ft. Like I said, seems impressive it's requiring that much fuel.

Was it at 100% duty cycle before adjusting the injector offset? Or did you change the injector constant too? I don't understand why injector offset would change it much since I thought offset was just how premature does the injector fire to get the timing right, I don't see why that would affect fuel flow.

 

At the 43 psi charting I would max out at 86%. My injector constant is set @.10 with an Inverse of 2.3. I did have my Constant in the .12's but my MAF Volts was getting out of wack trying to get more fuel. So I backed off and went back to .10. I agree something seems off for im mile high...... But trims are within 5, -3.0 and lower in KFB throughout so I'm not sure.

 

Lat run I logged at 7000' with 535's and the 76mm pulley mine maxed out at 89% DC at 5700rpm, holding mid 10's AFR. That's with boost referenced FFV and whatever injector settings @snivilous set it up with.

 

Interesting. I'm not sure why im maxing 750s at this point especially in thin air. Granted I need to lean out some but injDC is still up there

 

I'm not sure but I just assumed more pressure at the FPR with increased values at voltage pushes more fuel. Figured especially up in the 14/16 volt range where PE really kicks in and dumps fuel. But I have no idea and am just assuming and probably thinking incorrectly.

 

Check this out for reference. 100% DC, 0.0 knock, A/F @10.54

 

Time for those liter boys

 

Liter boys? It's purring like butter

 

Any of you crazy sobs shooting meth through this beast into the superchargers lower intake manifold lol

 

There was a build with a TVS 1900 Maggie that injected to each runner. Probably will be easier to do with this when it hits the market (aluminum version)
https://www.aesinnovate.com/product-page/3ur-runner-kits-v8-5-7l

 

That's pretty cool. I was curious on how folks were running meth figured spraying into the air intake after MAF. Didn't know if somewhere out there maybe drilled into their supercharger manifold and threaded in 9th port injector lol... Looks like the adapter would be pretty damn cool imo

 

They did I think I linked the build in this thread a few months back, trying to find the post.

 

Here it is @ARES35 :
https://hotrodtundra.com/2018/07/16/water-meth-injection/

Sorry better pics on this post:
https://hotrodtundra.com/2022/02/15/feb-2022-bring-a-trailer/

 

Dang that's a pretty cool setup there! I wonder how the meth is on the rotor coating, if they have a coating? None the less that's pretty sweet.

 

I don't think we ever got a straight answer about the coatings. Some say it is fine for the coating, cools the rotors, and seals better. I think it depends on the blower designer/manufacturer.

 

I've heard on some of the old school supers meth eats the coating. But I assumed these cases were for old tech, probably not the best wear coating compared to todays

 

This truck looks very similar to the truck that used to run at Bandimere speedway in Morrison..... He used to hold the record I believe. Not sure if it the same truck though

 

I think that still may be the case.