Anyone thought of running a weiand or B&M blower on a 350 TBI? I know you can elongate the middle 4 bolt holes in the intake to fit some 193 TBI heads. I have the TBI to carb manifold adapter plate. Which side of the blower would you put the map sensor on? I am thinking the engine side because it is possible to build boost at part throttle with a vacuum under the TBI which would be bad in terms of timing and fuel (more air, less fuel, and more timing could possibly burn a piston).

I am thinking the the vacuum compensated fuel pressure regulator would also raise the fuel pressure 1 lbs for every 1lb of boost and keep me from leaning out atleast initially.

See any imediate problems with this setup?

I am wanting it to just be able to run as I start tuning the engine.

Any easy way to use a 2 bar GM map sensor with a 747 ecm?

 

The MAP sensor would have to be on the engine side of the supercharger.

you will need more then a 1:1 ratio rase in FP, likely more like 2:1, at 1:1 you just overcome the manifold pressure, you do not increase flow at all.

no "easy" way to add a 2bar MAP, you are really better off going to either the 749 computer, or aftermarket. Even with BIG injectors, and raised fuel pressure, I doubt a 2bbl TBI unit will support the kind of power that unit can make, something like the 900CFM Commader 950 system is probably the way to go, 4 big injectors, more airflow, and a computer system that supports a 2bar MAP.

Searching would also yield tons of results on supercharging, IMHO, the roots style blower, like the 144, or 142, is the ideal way to go with TBI.

 

The injectors will still be in atmospheric pressure not manifold pressue because they are above the throttle plates on the intake side of the supercharger. Say I start out at 15 lbs fuel pressure and gain a pound of boost it will be at 16 etc. Anyone know of a 2:1 rising rate for a TBI system.

By the way the weiand and B&M are roots style blowers meant for a carb but their is no reason a TBI won't bolt on top of it with the adapter plate.

I was actually going to go with 454 injectors and like 20 psi to start with. I was thinking of using the GM style vacuum compensated fuel pressure regulator. I believe I will get vacuum compensation at idle and rising fuel pressure at boost ?

 

Physically putting a TBI on a blower shouldn't be too hard. I would also hook the Map sensor under the blower, but it's going to blind as soon as you get under boost. There is no way to hook a 2 bar map up to a 747 and have it understand that it's seeing boost.

You are in luck though, some one did get a 749 to run a TBI setup, and it can see boost, but I don't think that project was easy enough for a novice tuner. I don't know how comfortable you are with tuning, might be too much too soon. If your dead set on doing this one way or another, you might want to look into one of those FMU units. They are rude and crude, but if your giving your engine what it wants then it really doesn't matter how you do it. You could use your factory ecm to run part throttle and timing and once your under boost the FMU will add in the extra fuel via fuel pressure. It's not pretty considering what you can do with the 749 and $58 / $60 code, but there are lots of guys doing it that way.

I wouldn't even try to move this thing out of the driveway without a WB hooked up. With using this FMU and fudging things the way you'll have to, you need a reality check in the fuel department. As long as you keep the WB in the low 12's or high 11's then you'll be ok. Keeping your engine that rich is going to be a trip. You HAVE to get some 90 lb/hr injectors and run much higher than stock fp. I guess the FMU will be your friend here since it's going to be adding in fuel pressure. If your going to make over 400 hp, I wouldn't be surprised if you need close to 30 psi of fuel pressure. Also make sure you get the GM or newer holley injectors because the old chrysler injectors with the black tops that holley used to run won't take the higher fuel pressure.

Good luck and keep us updated.

 

With the 193 TBI heads and the vortec cam it will probably only make 320 HP @ 4,500 or so. I am thinking that it will make around 470 ft/lbs on the bottom end though.

What would happen if I used the GM 2 bar map sensor and shrunk the map table in half for regular non boost and half for boosted. Basically it will read 0-2.5 volts under atmospheric pressure and vacuum and 2.5-5 under boost.

 

I'd have to look at all the code, but there are many other things that the MAP sensor inputs are used for. And the computer MAY even give an SES light, when the MAP doesn't read up to atmo when it does its start-up check. It might even go to into safe mode. The VE's are just a small part of this, I'm not going to get into resolution, etc. A search will make your brain hurt if you search for resolution. But I don't know that is even an option. I have thought about trying it, just to see what happens, but I really doubt you could get the car to even start right.

 

Looks like I found some of what I wanted to know in the power adder section.

https://www.thirdgen.org/techbb2/sho...hreadid=253323

Someone has actually successfully run a MAP based supercharged TPI by rescaling the tables. All I would have to do is go 0-200 kpa instead of 0-100 kpa then change some of the other tables that use this. I know that the actual table will still say 0-100 kpa but it will be 0-200 in my mind. I will loose 1/2 the resolution but I will gain the boosted side. Resolution might be a problem but it would sure beat a MSD boost retard and FMU (IMO).

I know there is no way to just tell the ECM that I am using the 2 bar.

Only thing I am concerned about is that it might set a MAP sensor code when under boost due to the fact that a TBI ecm checks the voltage at start up and I believe that it believes that the voltage should not rise above atmospheric pressure.

 

On a side note I am not going to the blower for a while but was curious if I could make it work. I am spending time researching TBI chip burning and code writing and am far from ready for this project. I am however ready to tune the 350 TBI, w/193 swirl ports, and Vortec 350 cam though.

 

The tables in a tbi ecm are terrible. With the later tpi stuff you might be able to get away with it but with a tbi, forget it. The tables dont even have enough resolution for atmospheric operation.

The two options are to go romless and write your own code that takes boost into account, or switch over to a 7749. The tbi ecms/code are more suited to a tbi system but Im sure a 7749 could be made to run acceptably.

 

you can ran boost on tbi engine with no problems.most of the time without touching the map.if u do have issues you just restrict the vacumn that runs to the map and problem slove.trust ive called many companys,because i will be running a ati procharger soon at 9 psi with my tbi setup

 

That is a band aid fix and not the correct way to run boost on a TBi set-up. You would be shooting yourself in the foot this way. That is a lot of money to not do it correctly and get the most out of it. Chances are, JP, Dewey, and Dimented know more about TBI and boost than any blower company. TBI is like the skipped generation that no shop seems to understand.

 

Theres alot more to tuning with boost then just kinking a hose. 9 psi is about 60% normal atmospheric pressure, which is a sizable ammount of boost. Problem is that your fuel and spark maps stop at 100kpa. The map itself stops reporting at ~104.4 kpa, so there is no control over either fueling or spark when your under boost.

You could use an FMU, but that to me is a band-aid fix. I have a feeling those companies you called either only deal with carbs, or dont deal with boosted apps. at all. With a carb, the fuel is mostly flow referenced, but with a tbi, its strictly pressure, so you have to have a way to take that into account.

 

I know enough about boost and tbis to know that I dont know enough about boost yet to run it. Those guys must not know anything, because they seem to think theyre 'experts'.

"Hello? Whats that? Your gonna be running an intercooled twin turbo setup at 20 psi? Just unhook the hose to the map sensor and turn up the fuel pressure, itll be fine..."

 

I going to assume that he spoke with a blower manufacture, who told him to put a check valve in-line with the MAP, so that it cannot see about atmo. Then suggested he run a FMU.

I wouldn't consider myself an expert , but just like dimented, I know enough about both, that I am not going to mix them.

There are ways to do it RIGHT, it just costs a little more money. I already suggested the 900cfm holley unit, you can get it with a 2 bar map. It would be a good piece to go with a roots blower. I will also add, that a member of these boards did that, and STILL had some tuning issues. So if takes a lot of work and modifications, to get a system designed for this to run right, how are you going to do it with a system that was never meant for this.

 

The creator of WinALDL, known as Joby on the boards, runs a boosted crossfire Corvette with great success. I wonder how he was able to make it work as well as he did?

Steve

 

After looking at his website it looks like he just added a FMU and 90 lb/hr injectors onto his supercharged crossfire injected beast (almost TBI)