Injectors Vs Fuel Pressure

[brian617]

This is the first performance engine I ever build that didn't have headers. As good as this thing runs I should just upgrade. I started it with the O2 sensor out to try to feel any backpressure, wish I had a gauge. to me, it felt excessive, but with a dynomax super turbo, they do create backpressure. Everything runs so well, maybe it's just too restricted, I have the stock crap y-pipe in there yet too. that should probably go no matter what I do.


BLG

If you want to keep the Y-pipe look, for one from an earlier slip on cat truck, 88-92 I think. They have larger primary tubes, with 3'' collector. Even better than that are the 96-up 3/4-1 ton trucks with large dual pipes back to the muffler, that's what i'm using. The TBI truck manifolds are much better than the cars or even the Vortec trucks.

[BLG355]

Well stop doing this! Your running lean, the NB is not accurate but it's enough to tell you that your lean at WOT. So either adjust your PE fueling so the numbers get back into the .9xx or plan on melting a hole in a piston...

Is this the correct adjustment for WOT? I was reading that changing open loop settings only changes things before it goes to PE, then it uses it's own table...I think this is it.

PE AFR vs RPM.PNG

[EagleMark]

Yup!

But it's not always accurate depending on how many things are set up. If you make it richer it will go richer if the fuel is available.

[brian617]

To get those numbers to be accurate first the VE table has to be dialed right?

[RobertISaar]

accurate open loop AFR is VERY dependant upon correct VE, injector size and airmass temp correction.

[EagleMark]

To get those numbers to be accurate first the VE table has to be dialed right?

Yup, again something that has to be correct for PE AFR to be correct... or at least closer..

[BLG355]

Yup, again something that has to be correct for PE AFR to be correct... or at least closer..

Are these the right tables? I've been slowing getting the working the Injector flow size up and correcting the fueling tables using the excel spreadsheet, avoiding any WOT runs because right now it goes lean at WOT. it's getting very close, I have a few lower rpm cells that go into high 130's-140, mid-upper rpm stuff is close to about 4000 or so.

I figured I'd get this where it should be before I tackle the next item, is there any other fueling tables I should be watching or adjusting in addition to this?

VE Tables.jpg

[BLG355]

Has anyone had any experience with hollow cats? I am wondering if the hollow chamber of the cat is causing flow issues. idling tonight, I recorded 680 degrees directly in front of the cat, and directly on the back it is 440 degrees, if I move back 4 inches past the flange of the cat it drops to 260, and measures 200 at the tail pipe. I know it will loose a lot as it dissipates heat, but it seemed to be a short area where it drops from 680 to 260 and lose only 60 degrees the last 10 feet of exhaust. I think I am going to cut it out and put a piece of straight pipe in there since I am emissions exempt, it doesn't even have to look legit anymore.


BLG

[EagleMark]

Depends on how it's done for flow issues? I'd like a straight piece of pipe over a hollowed out cat.

As for the temps I think that is fine as it has a lot of room to cool there. Exhaust temps are of course hottest leaving the head but they loose temp fast through the pipe as it goes down stream.

[BLG355]

I didn't like the pressure i felt when i ran it with the O2 out, but without a gauge i don't know the pressure. Last night i fab'd up a adapter from 18mmx1.5 to 1/4 pipe, know i can run some line and put a pressure gauge on it. there may not be hardly any there, but without knowing for sure and before i dig into the engine more.

[Fast355]

Has anyone had any experience with hollow cats? I am wondering if the hollow chamber of the cat is causing flow issues. idling tonight, I recorded 680 degrees directly in front of the cat, and directly on the back it is 440 degrees, if I move back 4 inches past the flange of the cat it drops to 260, and measures 200 at the tail pipe. I know it will loose a lot as it dissipates heat, but it seemed to be a short area where it drops from 680 to 260 and lose only 60 degrees the last 10 feet of exhaust. I think I am going to cut it out and put a piece of straight pipe in there since I am emissions exempt, it doesn't even have to look legit anymore.

BLG

Not sure how much backpressure that a hollow cat would cause, but it certainly can reduce scavenging and hurt HP.

Even something as simple as pipe diameter and header design can drastically effect HP/TQ production.

This is a dyno of a Titan with a cheap pacesetter headers with unequal length 1 3/4" primaries into a 3" collector vs a titan with headers that have near equal length 1 3/4" primaries and 2.5" merge collectors. The 3" collectors and pipes MURDERED torque. Its not a backpressure issue rather a scavenging issue.

[BLG355]

I removed the hollowed cat shell and replaced it with pipe, the truck sounds so much better. But I still have glowing manifolds so it probably didn't to anything for flow, just sound. I did however make a discovery, I'll post a video.

https://www.youtube.com/watch?v=TljX...ature=youtu.be

So, who can guess what this means! , but at the same time I'm relieved because at least now I can fix what is wrong.

BLG

[RobertISaar]

i wonder if the two are related...... you clearly have a LOT of heat in the exhaust. i'm wondering if that caused the burned valve.

[BLG355]

from November until February, this thing ran very poorly. I tried working with TBI Chips and had zero luck has several chips and months of logging. I constantly has thoughts in the back of my head about whether or not I caused damage from that. I do know that it wasn't until after I stopped running his crap that I noticed I had glowing manifold, but who knows how long they were glowing. I'm not blaming it on TBIchips.com, but I ran countless logs with the truck running lean and missing very badly, trying to help him narrow it down. which we never did get his chip to work. the truck constantly would miss under a load he said it needed more fuel but it would foul plugs out in 10 miles! It wasn't until I found this place and got a start chip from mark that my truck was actually drivable. So it was abused from mega lean to super rich and everything in between for several months when it was new, I just hope this is the only damage I find. I ran a bore scope in the plug holes and everything looked good but the exhaust valves looked funny, so I figured I'd try the tailpipe test and that's when I found it. Hopefully it isn't too bad, I'll find out when I get the heads apart.

I rarely ever use manifolds, and this is the first time I put them on anything I built for more power. I could understand running it hard and not being able to remove the heat, but I was getting glowing running lower rpms under a load, so I figured there has to be something more to it. at least I hope.

BLG

[ony]

cam timming? might try one of them cam gears that you can advance or retard the cam timming.