Cdeez

Well I've been away from TBI for a while as I have been enjoying driving my 90 Silverado that I swapped a 6.0 with a S475 turbo into. Learning to tune the 3 bar speed density beast was fairly challenging but I got it tamed.

I'm finishing up a TBI project that I have wanted to build since I started messing around with TBI and learning the basics of tuning with stock and very mild SBCs.





Here are the specs:
355, flat tops, WND-7547-1 single plane intake, SUM-162108 heads,LUN-20080660 cam 279/287, Lift .447/.471, longtube headers. 7427 PCM

I'm thinking I need more fuel pump and injectors before I even start to tune this thing. Stock pump and stock injectors are in there for now..... I have a Walbro 255 laying around that I will drop in to take care of that. I believe I made the stock FPR adjustable years ago but I'm thinking I want to plumb in an aftermarket one with a gauge and that is easier to adjust versus taking the stock injector pod off to get at the FPR.

The two big questions at this point are what kind of injectors should I be looking at to fuel this thing up top?

And..... the VE is obviously waaaaayyyy off with these Summit(trickflow) heads, longtubes, single plane intake and the cam..... Wondering if anyone else has tamed a beast of a TBI like this before and could offer insight on a massive global trim to the whole fuel table to get it a little closer before I even start trying to dial in the fuel table????

Dominic Sorresso

On my 84 Xfire, I needed the BB injectors running fuel pressure of 10psi at idle and 20psi at
WOT for sufficient fueling and ~ 80% DC on the injectors. Don’t be surprised if u’ll need a
VAFPR. I used the Aeromotive 13301. And EBL to run that.
Car ran 13.3s and trapped 104.3mph w 3.45gears. IIRC it dyno’d 283rwhp/347rwtq.
Stump puller motor. ����
And btw, I was using the TF23d heads w a Comp Cam roller cam and full roller valvetrain.

Cdeez

Those are some impressive numbers for an "archaic" TBI setup. LOL. Just shows you what's possible with a TBI system.

I have a 7427 PCM and was hoping to continue to use that to control this thing. It's also getting an 80E so the EBL is not going to work for me on this application.

Fast355 suggested in another thread that my 61# injectors will work, but just to up the fuel pressure. He mentioned a marine TBI pressure regulator that would feed 30PSI which he used on a TBI setup of his with a Weiand 144.

How do you like that Aeromotive FPR you got?

Dominic Sorresso

Fast was helpful to me w my Xfire. But I moved on to DOHC world the LT5.
I can only tell u about my configuration. I was using 80# big block injectors.
At 10psi, they was not enough fuel for WOT, but cranking FP up to 20psi, made idle tuning very problematic. EBL solved that for me because it could vary the VE based on FP. The Aeromotive ran trouble free and connected to a vacuum port gave me 10psi at idle and went up to 20 for WOT which put me at about an 80% duty cycle for the injectors.

Fast355

iTrader: (2)

HAHA,
That makes two of us that have moved on to the DOHC V8 world. Except I like my VK56 engines. I have had 2 different Nissan Titans and now currently an Infiniti M56S. Something about having a luxury sedan 4 door boat that runs low 12s at over 110 mph and still knocks down 24 mpg highway at sane speeds.

Dominic Sorresso

Fast355

iTrader: (2)

For sure! In truck tune the older VK56 had cam phasing on the intake lobes only. Factory rating was 317 HP but that was a joke. More like 350 HP at the crank and the 385 TQ rating was equally a joke. After I opened up the exhaust, intake and tuned it to run 93 octane it was making 330 RWHP and 400 RWTQ on a dynojet with cams no bigger than what came in the LG4 305. The Infiniti M56S uses cam phasing on the both the intake and exhaust as well as Nissans VVEL system on the intake cam. That system uses an eccentric shaft and varies the intake duration and lift while the engine is running. Makes for one hell of a flat torque curve on an engine that is nearly 12:1 with direct injection. The M56 was rated 420 HP and 417 TQ but mine put down 378 rwhp and 390 rwtq stock. K&N drop-ins, 144*F thermostat, and 2* timing advance brought it up to 390 rwhp and 410 rwtq. Opening up the horribly restrictive luxury car exhaust to dual 2.5" with a X-pipe and magnaflow magnapack race mufflers brought the power to 428 RWHP and 434 RWTQ peak. That may seem like alot of work for the power gain, however it went from falling flat at 6,300 rpm to staying strong to 7,000 rpm. At 7,000 rpm I gained 100 RWHP! I picked up from 106-108 mph to 112 mph in a 4,500 lbs race weight car. The car had 4 cats, 2 resonators, and 2 mufflers along with 1 7/8" piping into a single 2.5" Y-pipe in factory form. Now it has 2 cats and 2 mufflers. It kinda blew my mind to trap 112 mph in a car that heavy on a stock OEM engine that had 120K miles with 120K mile plugs even. I feel if the electronics would allow for a gear/stall speed change I could really put down some good times even in that boat. The OEM final drive is 2.62:1 but the same car with a V6 had a 3.36 gear. I have enough room to physically fit P315/35R20s under the back. I have upgraded to a P275/40R20 from a P245/40R20 and still have to be cautious on the throttle in the lower gears.

Street Lethal

iTrader: (16)

... ever raced a big cubed/destroked SBC with that LT5 on the highway similarly cammed/geared?

- Rob

Fast355

iTrader: (2)

I have raced both a moded 6.2 camaro and a 6.4 Challenger on the highway. They tend t pull on me a little up to about 120 mph, then I start to walk away as I approach 6,500+ rpm in 4th gear. My 4th gear runs out about 140 mph and I go to 5th with is 1:1. When other cars go into OD they start to loose ground. For highway flying its better to have highway gearing and not have to use an OD than it is to have lower gears and an OD considering the amount of power it takes to spin and keep the driveshaft spinning at those speeds.

Fast355

iTrader: (2)

OP, sorry for hijacking your thread.

I did find you a high pressure spring on Ebay.

https://www.ebay.com/itm/GM-TBI-28ps...xUx5ZX&vxp=mtr

Dominic Sorresso

Fast355

iTrader: (2)

My stock standing mile was 157 mph and went to 159 with the grille opening taped up and the mirrors folded in. Not sure what the 1/2 mile was but the 1/4 was about 106-108 at that time period.

Street Lethal

iTrader: (16)

Since my local track closed its' doors on drag racing I was forced to lower my standards and attend a street race gathering not too long ago when we had some freaky (good) weather, which at first I wasn't looking forward to. To my surprise we had a really good time. Illegal, but good. SBC and SBF guys dominated (true street cars)...

AWD, 32 Valve V8, 24 Valve V6, turbo, didn't matter, they were dominating them and pulled way over 7000-RPM even without the nitrous, though equipped for it. I already knew, kinda, what was going on with them, and after awhile they started to come around and share their setups. Big bore, short stroke, correct compression levels and valve events, and you have a recipe that will annihilate a DOHC engine, especially when geared correctly. Valve-train parts get costly, of course, but hey, it's nice to see these pushrod engines still competing hard... and still winning.

- Rob

Dominic Sorresso

Cdeez

Hahaha no worries man. That spring fits in the stock TBI regulator huh?

Fast355

iTrader: (2)

With cam phasing that difference is even more dramatic. 22 in/hg at idle, table top flat torque curve and still pulling strong at 7,000 rpm. Try that with a SBC!

Street Lethal

iTrader: (16)

Haha, true to an extent, but there are of course ways around that as well, and today's SBC cylinder head and camshaft designs are no slouch, so cams high in duration are not really needed. There was a benefit to those 32 valve Dominion/Aero SBC heads once upon a time, but 16 valve heads keep improving which is why those 32 valve heads never sold well, if any. Mine pulls to six grand naturally aspirated no problem, while making good power, but of course needs the turbo to push it up any further than that, but I wouldn't need to at that point. Remember though, high RPM from more valves per cylinder allows to reach your calculated speed faster up top because of flow, but the way to make up for that is gearing with a lower revving engine, which is what Callaway used to take advantage of. So although you don't hear the engine screaming at say 8000-RPM with an LT5 while pulling to a high speed, you will still feel the same speed in an engine screaming at 6000-RPM with different gears out back, it just doesn't feel like it because the RPM is lower and you don't hear the engine, but the speed is still there because it is pulling just as hard. There's a really good video of an old turbo Callaway racing a turbo Supra that shows this, and while you can hear the Supra's RPM, which is what they are known for, the Callaway just walks right by it at 6000-RPM and 180-mph. People may say that the Supra can throw more boost, but then again so could the pushrod L98 Callaway...

- Rob

Dominic Sorresso

Street Lethal

iTrader: (16)

Haha, I'm not taking anything away from the LT5 it's one of my favorite engines. That Callaway above just shows how clever Callaway was by playing with gearing. But there are two ways to RPM to make power up top. More valves per cylinder, or with a big bore w/short stroke and correct valve events. The smaller the cubic inch displacement, the more radical the cam will sound, obviously, which is where the LT5 has say a DZ302 beat, much smoother on the LT5's side, and more street friendly. But more cubes for the SBC helps to smooth it out tremendously and this is where it gets different. A well built naturally aspirated street LT5 will trap in the 120's, give or take, but then again so will a well built NA DZ302 that screams to 8000-RPM. Now, increase that SBC to over 400 cubic inches while maintaining a short stroke and 8000-RPM ability, suddenly it's an entirely different ball game. LT5 can do the same, sure, but it would actually hinder it down low so there would be no point. This is why guys running over 400 cubic inch small blocks dominate at the street races, they don't build them with the everyday average GM stroke, and some run with full exhaust and are very unsuspecting. This SBC goes 5.70 on a 7.5" rear end, that is crazy fast for a street driven small block, and we know how they did it. Now, make the cam a tad more street friendly, and bring that 8 second 1/4 small block with full exhaust to around a 10 or 11 second 1/4 small block with full exhaust and run it against a well built LT5. Same pull up top for both. Most street SBC guys don't build for the highway though, some do though, but there's no money in it...

Cdeez

I have installed the 28-30 PSI spring in the regulator and fiddled around with the BPC a little bit to see what it might like..... It's running pretty poor now with that spring in there. Probably getting way too much fuel even though my wideband says 12ish... Still too rich for idle.

After putting that spring in the regulator, the injectors make a howling sound while pulsing, and the fuel pump sound WAY different compared to before. Also getting a fuel pump relay error after this.

Don't know what the fuel pressure is actually running at, I ordered one of the adapters to install a gauge and it will be here in a few days so I can nail that factor down.

I have been away from TBI for so long while dialing in my 3 bar 411 PCM S475 6.0 that I have become quite rusty with the OBD1 side of things.... It is commanding an AFR at idle of like 12 or lower.... I can't remember what table(s) are responsible for this?

Attached are several tunes and logs THe tunes are both using different experimental values of BPC since I'm not exactly sure what it should need. ANd the logs are when it was started and idling decent BEFORE the 30 PSI spring, and then AFTER the 30 PSI spring was installed in the regulator.

I can't upload log files. What was the trick to add something to the file extension I can't remember?

Cdeez

Turns out it was a TBI base gasket leak. Back to dialing this beast in.

Dominic Sorresso

Occam’s Razor.

Cdeez

Fast,

are you still here? What would you do to get the 27 PSI spring to idle without being stupid rich???? I can't find any consistent information on whether or not it is or ISN'T a "bandaid" to use a VAFPR on a PCM that won't really interface with one.

I'm doing some injector math and with an OLD PSI of 12 and a NEW PSI of 27, and an OLD FLOW RATE of 61 PPH the NEW FLOW RATE should be 91 PPH.... Will anyone confirm this please?