S10K20

I searched but didn’t see any about turbo a tbi.
I have the ebl for some time. I’ve been tuning a stock engine. Mostly changing small stuff and played with e85.
Now I have a turbo on and been learning in baby steps.
I've read that turbo on tbi is difficult or not possible.
This is a 2.8 running 45lb (4.3) injectors with areomtive vac/boost reference fuel pressure. Boost 10psi and running e85

AlkyIROC

What's your question?

S10K20

One would be that my nb O2 was fine before the turbo but first trip out it kept subtracting fuel until it was lean misfire.
Its located in stock position and turbo is rearmount. Wideband is in same place. I’m running open loop for now and nb reads full rich. Changed plugs last weekend and color was perfect.

Turbo has been on for little over 2,000 miles (5weeks daily driver)

Another issue is I was take it out the TPS at 6psi.I blame most on China BOV and now have Turbosmart. Since install of the new BOV I had it read 1% at idle off pedal running 10psi once but fine next day.
Im now at 12psi as of this morning after getting more fuel. I was thinking of extending shaft 1/2” and spacing it off TBI some. 2.8 TBI doesn’t have the L thing on sensor like the 4.3 and up.

Engine i I believe is 125hp stock. I assume I’m around 210hp with 12psi?
Clutch won’t hold 12 but was good at 10 so I’m done turning it up. I don’t have Intercooler. IAT is 12” before butterfly and I haven’t notice it over 115. Clutch is stock and replaced 2 months before turbo.

Like I said this was to learn the tuning side to apply what I learned to another engine. Reading online I couldn’t find much about turbo and TBI.
How much boost can a stock engine handle and keep taking it.

Fast355

iTrader: (2)

I would have found some 350 injectors myself especially on E85. I would also look into a 2 bar MAP sensor and the EBL. Your throttle shaft fuel leakage issue can be fixed the same way a boosted carb can.

I broke the crank on a stock 1987 2.8 TBI GMC Jimmy. I put a 3.4 into it from a 4th gen F-car. First with TBI then with the MPFI. Used the coil pack setup on both run by a 7427 TBI PCM.

S10K20

I should have been more clear.

I’m useing EBL flash with 2 bar map, TT-1 wideband for tuning.

Turbosmart BOV, Turbosmart boost controller, Tial waste gate. Turbo T3/T4




I know I could do something with throttle shaft leakage but since the new BOV and location I hadn’t had a problem in 3 days.

China BOV was 12” from butterfly and now have it mounted in spectre bonnet. The engine is not pernement.




Why would the nb read extremely rich? For what I’ve read it should be between manifold and turbo with wb after turbo.




As as far as the injectors the 4.3 injectors seem to be ok except duty cycle gets to about 105% with 12psi.

I dont know how much hp the engine is marking but I figured 350 (65lbs?) would be to much or at least off boost. The stock injectors are 33lbs.

How much hp would 12psi make on stock 125hp engine on e85?




It was my understanding that gm had several problems with the 2.8 and in1988 they used a stronger bottom end and oiling was improved.




Fast 355, how did you break the stock 2.8 crank? A buddy of mine also broke in that he babyed in s10 auto with less than 150,000miles. Truck looked new and was never beaten on. He got it when his grandfather passed away. Can’t remember if it was 86 or 87.

Over all I’m pleased with the way it’s running except I’ll be done at 12psi bc I’m not putting a clutch in it. Everything was bought for the new engine (except turbo) to learn with turbo wise.


Just mainly looking for someone that has done it with TBI and what there setup is and what problems they came across.

My ebl flash already has the extra injector driver so the new engine will 8 injectors instead of 2.

S10K20

Fuel pressure at idle is 13.5. With vacuum line disconnected is 21psi. so with 12psi boost should be 33psi with areomtive 13301.
Would 65 lb injectors he needed?
i know duty cycle should stay under 85%

S10K20

Everything bought for engine is for the new engine except the turbo.
I put in a 31 1/2 by 13 Intercooler. Also boutght a snow performance stage 2 meth injection for $75 (2 nozzles, pump,line, and progressive controller). I got before Intercooler install.
Afr at 13psi (boost creep) is about 13.8 with winter blend e85.
Engine was to learn off of and really only problem I had was tps and blame most in China BOV. I know I could have done mods to tbi but this was a genie pig and temporary engine to learn off.
I have learned a lot and hope I’m ready for the 350 once i get the 4l80.
With smaller engine and bigger injectors available is probably why I was ok with tbi. I was told tbi couldn’t be turboed but with only a 2.8 I had room to grow. Would not try it with healthy V8 and Tbi.
Dont seam to have problems with the 4.3(45lb injectors and would have tried the 350(65lb) but I only have 2.8,4.3,454 injectors. It would get to 13.5 afr at 9psi but used meth to help it to 13psi.
Truck is actually fun to drive 8psi and higher ha ha.
Only complaints is if I stomp it from say 2,000 it don’t care for the 20 psi fuel and no boost, also the salvage pump as I don’t have a light or anything to let me know if it’s on. I have it tied with fuel pump power and sioniod but used a d/c circuit breaker I wasn’t using on my solar and I would lay something on it and didn’t notice till I pumped oil out twice ha ha.
Dont know if it’s just tough or bc it has 299,xxx miles and bearing clearance high biur still holds 45 psi down the road at 2,200rpms.
Idle hot in the 30’s

Kevin91Z

iTrader: (1)

The biggest problem with TBI is two injectors cannot feed enough fuel to make more than about 325-350 horsepower at the flywheel. Even the 65lb injectors, or larger.

65lbs x 2 = 130 lbs

19lbs 305 TPI x 8 = 152lbs

You have less fuel than a stock 305 TPI engine.

You need some kind of aftermarket TBI unit with at least 4 injectors, or preferably just swap to a multi-port setup with 8 injectors.

GeneralDisorder

iTrader: (1)

As to your O2 sensor question - the sensors read differently when subjected to the back pressure from a turbo. That's why all stock turbocharged applications I'm aware of have their O2 sensors after the turbo.

GD

Fast355

iTrader: (2)

You can feed 500 hp minimum from 2 injectors using all stock GM parts. Closer to 700 hp if you get the Brazilian alcohol injectors.

88RS

iTrader: (7)

Where does one acquire said Brazilian injectors? Are Omega and Opala Chevrolets? With the 4.1 L (250 cid) I6 only? What trucks?

Not meaning to derail thread, this came up and I'm curious from past reading.

S10K20

I’m curious my self about the Brazilian injectors my self




Im running open loop and have check my plugs twice and everything seems to be in order.

Iv read about pressure sending wrong reading with WB o2 preturbo but I though nb stayed before turbo? The nb is what’s way off normal driving. I’m using TT1 with the sensor Rbob sends.




I’ve got about 5,000 miles on the turbo.




How much hp would 13psi on a bone stock 2.8 v6 be making? Based on what I see with plugs and the WBO2 (in wrong place) and injector duty cycle I assumed about 230ish. This is with the 45lb 4.3v6 injectors at 33 psi fuel/13psi boost.




I do do have the extra injector driver for 4 injectors but I’ll use 8 low ohm with the new engine




Speaking of the low ohm injectors, what came with them from factory?

GeneralDisorder

iTrader: (1)

Well the narrow band O2 isn't going to be much useful under boost but if you have much more than 3-5 psi backpressure on the sensor it's readings will be skewed. At no-boost cruise and idle it should work ok. It's readings are meaningless under boost though. Should be useless anyway being a narrow band.

GD

S10K20

No boost cruising was subtracting fuel to the max till it would miss fire.
Didnt have any problems before installing the turbo. It got so bad I was driving just hard enough to keep it in pe then coast and back into pe all way to work. I couldn’t forgive it out on way home so went to open loop and have kept it this way.

GeneralDisorder

iTrader: (1)

Well pressure in the exhaust will cause the sensor to read rich, and with a narrow band sensor, ANY skew due to even light pressure is going to throw the sensor WAY off because they are highly non-linear sensors. And the ECM is looking for the signal to cross the zero point and begin cycling in response to its fuel algorithms. It doesn't see that, it just sees a perpetually high voltage and starts pulling fuel till it hits its max lean trim but the pressure is still there.....

Check your pressure on the O2 port. Cheap turbos have very poor efficiency ratios. That is the ratio of compressor wheel pressure to turbine wheel backpressure. Older inefficient or poor tolerance turbos can be 1:3 or worse.

GD

S10K20

Thank you GeneralDisorder

This is my first turbo I’ve done or been around. It is a China turbo T3/T4 ,compressor inducer 50.5mm, turbine exducer 55.9mm, turbine A/R .63

I knew in back of my mind that o2 uses pressures but never put 2 and 2 together. Never thought about the back pressures in this way. Feel dumb.

So if I understand this right I should remove the NB o2 and install pressure gauge? Compare exhaust pressure to intake pressure?
what ratio should I look for? And how could this be corrected?

Down pipe is 3” and mabe 2’ long
New engine will have a good turbo but with this engine I went with the China bc I wanted to learn with this engine without spending too much.
So far I’ve learned a lot but not nearly enough

GeneralDisorder

iTrader: (1)

Right you can just remove the O2 sensor and install a mechanical vacuum/pressure gauge such as would be used for Carburetor fuel pressure and intake vacuum diagnostics. A good free-flowing exhaust shouldn't show much for backpressure - 1 to 2 psi even at cruise RPM (light load). Anything more than that is probably going to negatively affect O2 readings.

It can't really be *corrected* without some pretty fancy re-writing of the closed loop ECM micro-code. It would have to be able to mathematically correct for the expected pressure at every RPM/engine load that is desired to be in closed loop... it would take tables and calculations the ECM is not currently equipped with.... Better to just relocate the O2 sensor after the turbo. Either that or just ditch closed loop altogether - which is kinda a pain with speed density because of all the ambient conditions that skew the IAT readings, and so forth. It's tough to tune it so that ALL ambient conditions are spot on with fueling. The closed loop helps A LOT with managing speed density's proclivities for being stupid.

GD

S10K20

I’ve been open loop since about 2 days after the turbo install.
I will check pressure at the exhaust. Thing is it’s all stock exhaust expect cat is gutted and no muffle anywhere.
Could the intake path from compressor side of turbo to engine be restricted and cause load to exhaust side at turbine to create restriction?
Did I get the wrong turbo?

GeneralDisorder

iTrader: (1)

I've never experienced anything like that. I don't think you got the "wrong" turbo. There's not one right answer for turbo size depending on the goal. A better quality turbo *might* not have as poor of a ratio and *might* not cause these cruise problems. But without data it's hard to know for sure. Is it a major undertaking to just move the O2 sensor to behind the turbo?

GD

S10K20

Not to much to move it I don’t guess. Turbo is under the bed just behind cab. Mabe extending wire 5’ and using 3 wire sensor.
Reading about exhaust pressure vs boost pressure. Never thought about it but it all makes since. Thank you for pointing it out. I still have a lot to learn for sure