VVTi UZ into 1st Gen SC400 Project

[spdrcr771]

Shawn, with due respect to you and David, I wouldn't try to convert a return type fuel system to be returnless, by simply capping off the return at the fuel rail.

At best, your fuel pressure is going to be way higher than it should be, which will cause the injectors to squirt way more than they should and the engine is going to run extremely rich. Not to mention having one very confused ECU that will not be able to figure out what's going on, and will probably go into limp mode. You'll also probably burn your fuel pump up shortly, as it won't appreciate pumping "dead headed", with no outlet other than the injectors.

The simplest returnless systems are not "truly" returnless because they simply relocate the FPR at the pump, inside the tank, and they just run the output of the pump at the required 43 PSI, and return the rest directly in the tank. This isn't as good as having a manifold reference line running to the FPR that keeps the deltaP across the injectors at 43 psi, instead of just the fuel rail at 43 psi, but you might get away with it for an engine running at atmospheric. No way would this work for a boosted motor.

The fancier returnless systems incorporate some sensing electronics to control the pump output to have the correct deltaP across the injectors at all pressures (atmospheric and boosted).

If I were you, I'd figure out a way to convert the VVTi motor's returnless fuel rails to a return type, then I'd put a conventional FPR there, and hook it up the usual way. I don't think the ECU will care, and the injectors will be getting the correct pressure across them.

L O L that right there kinda just went over my head, but makes sense. I dont know much about adjusting fuel pressure, & making sure it stays right. Im glad im not having to do this on my build. I like having returnless & no egr on the vvt-i, Less stuff to have to mess with, when having to do a build like mine. Also one less thing to have to mod when i did my S&S header install.

 

[Lextreme II]

If I were you, I'd figure out a way to convert the VVTi motor's returnless fuel rails to a return type, then I'd put a conventional FPR there, and hook it up the usual way. I don't think the ECU will care, and the injectors will be getting the correct pressure across them.

You are right John. Matter of fact I was going to create a return line from the fuel rails. I think using the older rails might work but I need to double check. Thanks

SPF: I found a 1998 SC400 ECU for you. Dont know why but I brought an extra few years back. It has been sitting and collecting dust.

 

[cribbj]

If the end goal is to have a returnless system, then the cheapest way to do it is to find an FPR that's suitable for total immersion in the tank and hook up your '93 pump to it. It'll take a bit of experimenting to get it right and in the end, you'll still have a richer idle than you want. To do a returnless system correctly, you'd probably need the tank, pump, fuel pump ECU, etc.

But if your goal is to get the engine running, the most practical way is go back to the traditional return system. Just modify the VVTi's fuel rail by adding a return fitting, then hook up a conventional FPR, and your existing return line and you're done. Everything else in your car is setup for a return type system, so it's simple.

This is the most practical solution, unless I've missed something?

And if you modify the fuel rail with an eye to the future, you can always remove the return fitting, or just plug it off, and voila, you're back to a returnless system on the engine itself.

 

[spf_lexus]

Criibj

I'm already checking out parts. Problem is, 92 has 2 "bridges" that link each rail together but the 99' has a single bridge in the back. I wonder if there is such a thing as a "double out" banjo bolt. If I can make a "T" at the rail bridge, im pretty sure it can work. This way everything stays simple. I have my old rising rate FMU, and I believe it can be setup for atmospheric... I think mounting this in the fuel return line would work very close to having it rail mounted.


Are you postive the 99 ECU doesnt control the fuel pump tho? Seperate ECU? If the 99' ECU controls the pump all I need is the OEM tank/pump (with it's included FPR) and this would be the fastest/trouble-free solution.


Lex-

Thanks man, have fun on your trip. I'll probably take a couple days sourcing parts anyway so i'll give you a call Monday.


spdrcr771-

Old tech meets new tech.. I knew that I was bound for a mechanical disagreement eventually . Returnless systems send fuel from tank based on engine load and only sends what needs to be burned. While the early system has a fixed fuel presure that constantly flows fuel in/out of the engine and only changes "overall" pressure. Returnless systems exist to reduce hydrocarbon emissions by eliminating heatsoak, where the engine heats up the fuel to a vapor. I'm curious to see how large the carbon canister the 99 SC is (if it even has one lol)

 

[spf_lexus]

Cribbj-

The more I re-read your 1st thread the more I want to find an aftermarket "internally bypassed" fuel pump. If it wont burn out by having a higher base pressure, I dont see any harm and using the 99' pump?

 

[cribbj]

Criibj

I'm already checking out parts. Problem is, 92 has 2 "bridges" that link each rail together but the 99' has a single bridge in the back.

Draw us a pic of the two rails, the bridge and where the fuel comes in.

Criibj
Are you postive the 99 ECU doesnt control the fuel pump tho? Seperate ECU? If the 99' ECU controls the pump all I need is the OEM tank/pump (with it's included FPR) and this would be the fastest/trouble-free solution.

I would almost bet the ECU doesn't directly control the fuel pump. Toyota just doesn't do things that way (or they didn't used to). The main ECU has all the sensitive signal stuff, and there's probably a 2nd fuel control ECU with a honking big transistor or thyristor in it to control the speed of the fuel pump. It's quite possible, the PWM circuit is in the main ECU, and it sends the signal at a very low "logic level" to the fuel pump ECU which then "amplifies" it to handle the 10-20 amps that the fuel pump draws. I'll have a look at the VVTi wiring diagrams and see if they give any clues.

 

[spf_lexus]

I'm guessing the 99' pump has a vacuum diaphram with a vac. line running from the pump to the manifold?

 

[spf_lexus]

Just realized the "missing" front bridge has 2 threaded caps that could be drilled out and tapped for a small return line (on either side) but since it only has a single bridge, would I have issues with bank 1 getting more pressure than bank 2? Or would a single fuel bridge be enough to regulate both sides? I think its possible to run a steel braided line under my TB, to link the 2 rails at the front, and from there i could add the FPR.

 

[spdrcr771]

Im not sure if this is the canister that you were talking about, but this sits under the intake manifold & has vaccum hoses that run to the diaphram that control the 8 butterflies inside the intake manifold.

 

[spf_lexus]

carbon (activated charcoal) canister is used for EVAP system for reducing hydrocarbons from the fuel system. I think the black "canister" in the 1st pics is for holding vacuum for the butterflies. Im guessing at 4000 or whatever rpm's with the engine at WOT, there wont be very much vacuum available to keep them open. Just a guess tho.

 

[spf_lexus]

So I was forced to take a small break from this swap but I think the fuel dilemma is going to be easier than I thought.


I have a 91 uz sitting next to my 99 uz so comparing systems is easy. The threads are the same for each rail and I think i'm going to just take out the banjo bolt that holds the bridge together. Then use the 91 fuel regulator/return fitting and thread it in place of the "bridge bolt" from the 99. This way I dont have to mod a single thing, and it effectivley changes to the return line type.

I'll post some pics later today.

 

[Thermactor]

Is the car in ca or co? Ive touched down in san diego and I want to check out your project

 

[spf_lexus]

It's in CA. I live in the Inland Empire. Look up Murrieta CA. Myabe this weekend we can plan a date where you can come over and check it out.

 

[spf_lexus]

I just hate it how I cant edit my posts any more.



Just realized how "wrong" that last line sounded LOL. Maybe this/next weekend if I have time we can schedule a meet.

 

[spdrcr771]

Hows it going man. Havent heard from you in a little while.

 

[spf_lexus]

The engine is swapped and installed, just waiting on the shifter stuff and alternator thats in the mail. I still need to take my fuel rail end cap to a machinist to have the old fuel reg tapped into it.

 

[spf_lexus]

New problem:


99' tailshaft has longer mounting flanges than 92' and d-shaft bushing wont fit. I already have the trans/engine in the car but I think I can unbolt the flange with a deep well socket. Its BIG.... like 24mm or larger.

 

[spf_lexus]

Does anyone know if the tailshaft yoke is threaded clockwise or cunter clock? Its really on there and I dont want to break anything.

Sean

 

[spf_lexus]

No big deal, had to man up and just stomp the pry bar with my foot but it was counter clock wise to loosen.

I managed to source a set of 1995 rails w/ attached fuel reg/return and it bolts up perfecty to the 99. All I need to mod is a steel braided "bridge" that can run above the TB since there is no room underneath. Heading to G&J tomorrow for the lines.

All I ned is my alternator (In the mail) and my shifter stuff and hopefully a 1st start this weekend.

 

[spf_lexus]

Ok, yes big deal...


The 99' yoke has a larger ID or "more splines" than the 92 so i'm back to square 1. I dont know if the 92 tailshaft will work out since it has 2 sensors and the 99 has 1. If all else fails I could just pick up a used complete 99 d-shaft and it will fit.