V8 swap questions - CPI to TBI in a 95

[Mr_Roboto]

Shouldn't need to use a TBI pump, I mean it can't hurt to toss it into the tank but conversely the TBI guys who are bumping base FP to deal with increased power install a TPI style pump. I have a 190 Gerator style Walbro in mine and it never gave a prob when I ran it that way. I bumped pressure up to 13 PSI but it ran at 11 forever. Also didn't drop down 3-4 PSI like my stock pump did when you hammered the throttle.

[Gordon]

if im not mistsken the tbi pump is 12-15psi and the tpi pump is 50-60psi.

99% positive that the tbi engine couldn't handle that kind of fuel pressure???

[Mr_Roboto]

The injectors lock at 30 PSI. The system uses a regulator that bypasses the extra fuel however. My 190LPH walbro was running fine at 9-13 PSI.

[rlsllc]

This is purely speculation, not fact. Any input would be golden.

Pressure is only possible with restriction, at least to some point. The regulator will open and close as needed to to maintain it's calibrated pressure, so if this theory holds true, it shouldn't hurt to run the CPI pump on a TBI.

What would be interesting would be to compare GPH at a given pressure. I don't know much about this, but I have an idea and would like to learn more.

[Gordon]

sooo... putting my cpi pump back in should net more hp?

[Smiliesafari]

Doesn't quite work that way. Fuel pressure regulators have their limits also.

[Mr_Roboto]

The TBI pumps work up to 15 PSI. Fine for a stock engine and then some. The reason you need to go to a bigger pump is if you do modifications. If you have more air you need more fuel to make more power. If you run too much fuel you will make less power. It's not like a funny car where you toss in as much nitromethane as you can because it carries its own oxygen.

ED:The reason some of these people run 30 PSI is because the engine makes that much power. When you're trying to make 400hp you're gonna need some more fuel. This can be used as a way of tuning for people that basically spend their time at wide open throttle, but is far from optimal for this and is even less optimal for low/mid throttle operation (eg it will likely be very not driveable for it and a tune will make more power.)

[Gordon]

Anyone know if this engine / trans (1995 obd 1.5?) can be tuned using the ALDL method?

My shift points are crap... shifts at 4000rpm at WOT.

[lockdoc]

Pounds per hour and high pressure are two different things. You can not use a CPI fuel pump with the stock TBI fuel pressure regulator. Go ahead and try if you want but so much fuel will dump into your engine I doubt it will even start. I used a high pressure unit in my 350 setup cuz I found one real cheap and I needed a bit more pressure at high RPM's than the stock TBI pump could deliver. I used an external regulator to bring the pressure down to around 13psi. It was barely able to bring it down that low.

The 95 TBI is not the so called OBD 1.5. That is only on multi-port injection systems in 95 like the LT1. Everything is on the removable chip and can not be programmed via the ALDL port.

[Gordon]

So you could remove the chip and have it reprogrammed for better performance and higher shift points?

Does that chip also control transmission line pressure?

I'm really tempted to rip this POS 4l60e out and toss the 700r4 trans i have here into it.

The 4l60e just seems so.... soft. Soft launches, soft shifts, low rpm shifts at wot, etc.

hmmm... stage 2 shift kit + vet servo into the 700r4 first.... then into the van... muhahaha


Still need to find a G80 locker or some type of locker... i believe this van is a 10 bolt 7 15/16" but pls correct me if im wrong.

[lockdoc]

The 4L60E is nicer IMO. Just get a custom chip from TBIchips. Plus you can put the stuff you mentioned in the 4L60E as well.

[Mr_Roboto]

Moates makes an adapter for the 95 style ECU. That being said I don't know if I'd want to bother with it. Do you have emissions compliance where you are? If so it may be best to keep the 4L60E and hack the box depending on regs. If it was OBD-II I would definitely say that because most places just hook it up and let you go if you don't have any codes.

I ran a Walbro 190 forever in my TBI vehicle and never had a problem. There are plenty of people on thirdgen.org that will vouch for the experience as well. It stayed at 9 PSI no problem either. A pinched return or a bad vent could cause issues like that.

http://www.moates.net/product_info.php? ... cts_id=126

[Gordon]

no emmisions here ( cat went bye bye a long time ago..lol).

I do know there is a vac line off the canister on the drivers side that says "to intake" i beleive.

Just need to buy a few T's for all these vac lines.

[lockdoc]

A standard Walbro 190 isn't considered a high pressure pump. It's rated up to 40 psi. Maybe 50. It's a High Volume pump. It would not run a CPI engine very well if at all. The Walbro 225 has the high pressure option exceeding 50 psi. Like the CPI pump. That is what I used. And let me tell ya, a TBI regulator ain't no match. I was a afraid I blew up my injectors.

[Gordon]

What can cause a lag i guess at WOT?

When i hold it to the floor at highway speeds it's almost like it's not getting enough fuel but the pressure is steady at 10.5 psi... at idle it's 13psi.