Is it possible?
I could really use the hood clearance right about now. The holley 1" adaptor plate doesn't work well under my stock hood and I don't feel like spending $400+paint for a cowl hood. Does anybody have any information like a website or a company that sells an adaptor. The only problem I see is controlling 4 injectors with the GM drivers.
I thought I saw a website once that showed how to do it but I can't find it anymore and I've been searching for about a week now with no luck.
I just called up Holley and got the run around about how they have no idea but to call so and so.
I called a number Howle or something (got number from Holley) and he said that I could just run the injectors in series. Is that true.

------------------
, Jon (350 TBI!)
91 Red My website

 

Jon, this has been discussed before. Grumpy did a test and found that the injectors start to get flaky around 3k RPM. However, a simple injector driver can be built to drive four injectors that wouldn't cost more than $10-$20. JoBy drew up the schematics a while back - maybe I can find them again.

Past the injector driver issue, I don't see a problem with it.

Ken

 

I've been searching and still have nothing.
I'm worried about that flaky injector after 3000

 

Howell's, and several other folks have just wired the injectors in series parrarel, so you then have a 12v injector trying to run on 6v. I've know at least 6 guys that tried that, nope you can get them to go to again about 3K and they get flakey.

Their injector sizing is also a mystery. (4) 75 #/hr injectors is good for almost 600HP. Getting a short enough pulse for them to idle right is going to be really rough.
If you change to smaller injectors, and run an external injector driver, and then start from square one, you MIGHT get it right.
Would be ALOT of work.
For up to 350 the 454 TB and big injectors will work great. I know that not what your looking for, but just what will work.

 

Which is it, series, or parallel? (I assume you mean series?) Strange that they'd do it that way and sell it, for that matter!

Definitely a lot of work, but it would pave the way for so many others that want to do this. I don't think Jon is the first to do it, but if he went this route, he'd be the first to do it RIGHT. Question though, where would you get the smaller injectors? Does Holley sell smaller ones? Aren't they Chrysler injectors? I'd imagine you could get some at the junkyard but I don't know how much I'd trust them.

This is the route I've been considering taking with my '73 Vette. Slap a 2" 2bbl (454) TBI on top of a single plane manifold or a CrossRam (an Offenhauser, not a CrossFire!) manifold. I remember reading somewhere that a single plane manifold needs less airflow for the same amount of power (since it can draw from both barrels, instead of just one in a dual plane) or returns more power for the same amount of airflow. I would think a CrossRam would help make up a little bit of the lost low-end you might lose with a single plane manifold.

Ken

 

Grumpy, I understand it's going to be a LOT of work. I might even need some HELP but isn't that what this board is for .

------------------
, Jon (350 TBI!)
91 Red My website

 

Oh yeah, and by the way, even Holley tech people couldn't help me and I found THIS on their website.
http://www.holley.com/HiOctn/ProdLin...I/534-122.html

------------------
, Jon (350 TBI!)
91 Red My website

 

take 2 injectors and wire them in series, and use this pair as a single injector to the ecm. Then the other two injectors in series and wire them to the other injector driver, so then you have a series / parrarel circuit.

I've run Q-Jets on a GM cross fire with excellent results (and alot of stares).
Matter of fact going to do a 454 TBI TB to replace the Q-Jet soon.

The original Cross rams have a ton of plnum volume, and you'll need alot of AE to cover it.

 

I've seen that too. They don't seem to be the brightest bulbs in the pack, do they? you'd think they'd know their own products.

AE? Acceleration Enrichment? (Pump shot, I assume?) I've heard about that - you need more fuel to help fill the plenum, otherwise you get a bog.... (?)

Ken

 

Holley really looks to be trying to get into the EFI market, but they aren't advertising, and well their tech department, just ain't a tech enough.

There are several things.
Fuel trails air flow changes. With a large volume plenum, can get tricky balancing them. The sudden change in vac levels, changes the way the fuel wants to vaporize. Also, with TBIs, the shearing action at low throttle openings, has a huge effect on atomizing the fuel, and you lose that at higher throttle openings.

I always thought a crass ram would be fun, but after using the cross fire, figured it would be just overkill for most any street engine.

 

How about running the 4 bbl with 2 large injectors instead of 4 smaller ones.

Or

build an injector driver using a 8746 as a blueprint.

http://www.cruzers.com/~ludis/schematics.html

http://www.cruzers.com/~ludis/1228746sheet5.gif

Looking at the schematic there don't seem to be many parts needed.

 

I was actually looking at the driver IC itself. http://www.national.com/ads-cgi/view.../LM/LM1949.pdf
Grumpy, do you have any sources that I can e-mail about this?
edit: I noticed that this driver runs on 5v, not 12, or am I looking at the wrong source voltage?

------------------
, Jon (350 TBI!)
91 Red My website

[This message has been edited by JPrevost (edited October 13, 2001).]

 

Why reinvent the wheel? Just get a shorter adapter plate. I run a 3/8 inch adapter plate that any machine shop could make. Works fine for me

 

1949 been dead forra a long time.
You need one of the Cherry Semiconductor jobs. Either the 453 or 451, I forget which is the TBI injector, and which is the port version (Both are Peak and Holds, the injector resistance is different)

 

Yeah, shorter adaptor plate = 5/8" more hood clearance but I really need the whole 1". It is really that close. I had to cut the underbracing of the stock hood just to get the proflow unit to fit! Not to mention I had to cut the proflow up a bit just so the underbracing for the foam wouldn't rest on the injectors.
So pablo, now what would you do? $$$ for a hood for $$ for a 4 barrel TB. Besides, either spring or summer I'm going to an hot cam to hopefully make 400+ hp .
Grumpy, thanks for that update, now do you know anybody or a link to an inline injector spliter? Or how I would tap into the current drivers on the ecm? Anybody know some phone numbers of some people that might be able to help me?

------------------
, Jon (350 TBI!)
91 Red My website

 

I would go with the hood in a heartbeat, why make things hard on yourself for no reason? besides, cowl hoods look badass in primer so subtract the paint costs

 

Make things hard for myself...hahaha, too late, I just swapped in a 350 and kept TBI AND THE 8746 ecm. Probably should have gone to the 7747 until I got the handle on this eprom programming stuff. Not easy when you have to "find" things in a hack file and edit your tdf file just to find out the hack file doesn't even have the correct convertion values!!! oh well, the hack was free so I can't complain about that, just how you (Pablo) said KEEP THE 8746 .

------------------
, Jon (350 TBI!)
91 Red My website

 

I'm a little upset with Turbocity. Read this e-mail conversation and tell me if something doesn't look right.
"Hi John,

With all due respect, we try to keep our future engineering etc. under the hat. I'm sure you
can understand.

Vic


At 01:06 AM 10/16/01 -0400, you wrote:

I understand that the kit didn't use the 8746, but this is very similar to the 7747 which I'm sure was used in the kit. Every TBI ecm from the old crossfire to the newer 95 trucks used an ecm that only had 2 injector drivers. I'd like to know how the kit was able to control 4. I did some research and after about 3000rpm the injectors (if ran in series) start to get flaky and drip fuel instead of a nice spray (not enough power). Do you guys have any plans or information on how you actually hooked up the 7747 ecm to control 4 injectors?
I know that Holley has an injector controller box but I'm just trying to get some ideas before I go ahead and try it myself. I might eventually end up building my own injector drivers from an old ecm but I would like to gather as much information before going that route.
Thanks for the reply, Jon Prevost
----- Original Message -----
From: Turbo City
To: Jon Prevost
Sent: Monday, October 15, 2001 7:50 PM
Subject: Re: dual TBI custom question


Hi Don,


Sorry to say, but we have discontinued the dual inline TBI kit. Our kit didn't use the 8746 ECM.


Please keep in touch,
Vic


At 11:47 PM 10/12/01 -0400, you wrote:
Okay, I'm pretty experienced with TBI but my new project is getting a stock GM 8746 ecm to control 4 injectors instead of the normal 2. If I hook them up in series then the injectors get half the volts (6v) each and that is okay for under 3k rpm but it doesn't work above that. This isn't good, so I'm e-mailing a bunch of well known EFI companies to ask them for some kind of injector drivers. From your website you show a dual TBI kit that runs dual 2 barrel TB units. This is pretty much the same thing I want to do but it'll be with my holley pro-jection 4 barrel.
The only reason I need to do this is hood clearance. I don't feel like getting a new hood so the only way to get rid of this 1" adaptor plate is to go with a 4 barrel unit. Besides, it looks like a fun project :-)
If you can help me find any information I'd greatly appreciate it.
, Jon Prevost"

Basically I need help, they COULD help me, but it's "under the hat." What kind of BS is that considering they stopped making the kit already! Do they expect everybody that wants dual TBI to go to their inhouse custom garage and pay $$$$ to get it done? I'm really kind of upset with the inability to at least provide some substantial information. This makes me wonder why they stopped making the kit. Maybe because they wired it in series and were getting complaints!??!!?!
Oh well, just had to vent, sorry.

------------------
, Jon (350 TBI!)
91 Red My website

 

Actually, I looked at this too - is it me or did the ECM look more like a '7730-ish ECM? The connectors came out the side, seemed like. Then again, the pic was pretty fuzzy. You're right though, they probably discontinued it for two reasons - one, they couldn't get it to work properly (complaints maybe?) and they probably didn't have enough market for it to begin with.

Just my guesses from observation..

I've asked Turbo City some simple questions before - like the size of the CrossFire TBI upgrade - they wouldn't tell me it was 2". Kinda silly, but then again, they are a business.

(BTW, it was the same "Vic" guy that answered me.)

Ken

 

I just find it funny he said keep in touch and then "future engineering" like TBI was THEIR future....lol. I'm still confused by his reply but I understand where he's coming from (just don't have to like it).

------------------
, Jon (350 TBI!)
91 Red My website

 

Edelcrock uses the 7747 to work on their muti port systen with 8 injectors. I think they said something like they set it up for double fire.

------------------
Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
Cam change:TRW 198/210 ,450/.460 114 LSA
Stock TBI manifolds
'85 IROC Ex.
14.94-92.00 mph
SPDC base and "350" Vortec coming soon!
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

 

The computer that looks like a 7730 and can fire 4 P/H injectors is the 7749 from syclone and QUAD 4. The Q4 used 4 P/H injectors stock. Getting this to run correctly in your application will be challenging.

HTH

John

Heart of Texas Power and Performance

 

8 saturated works out to 2 TBI P+Hs electrically. So it's a no brainer to do that. In their chips they really just tinker with the AE because of the manifold differences.

 

Sorry, but that's a no go too.
TPI P+Hs are 2.4 ohms
TBI P+Hs are 1.2 ohms.

Given time and rpm you will take the injector drivers out.

 

So Grumpy, I can run 8 Magnetti/Marelli saturated injectors with the 7747 ECU that is running two TBI peak and jold injectors now? How do I wire the injectors up??? 4 in parallel to each driver (or TBI injector wire) or 4 in series with said driver???

How can I know that I am safe before I do this? Can I measure the resistance of the injectors or something? Does that have any meaning in this mess? ie, what resistances do I need/want?

Also, are all TPI or Mag/Marelli injectors sat injectors or are some P+H and how can you readily tell the diff?????

 

http://www.onsemi.com/pub/Collateral/CS452-D.PDF
I found this, it looks like Cherry has renamed to ONsemiconductor. It says for the low impedance injectors ~1.2ohm, use the CS453 ic. Looking good, now I need to figure out how the stock ecm drivers work and I should be set.
Thanks Grumpy for the heads-up


------------------
, Jon (350 TBI!)
91 Red My website

 

Just remember at WOT, they are on alot of the time, so they get prety darn warm.
I've run some we'll just say different things, and had ecm case temps of 120dF. That's not enough you can't hold it too long, and too hot for the electronics. The switch poorly at too high of temps..

This is when your to the stage of needing to run one on an ecm bench for a few days, to make sure it doesn't fail in traffic. Seriously.
I've tested alot of ecms to distruction, and some of the bullet proof designs aren't what some folks think they are. And remember what ever you do, you need to do two.

 

Thanks grumpy, I was thinking about the cooling and I have a bunch of heat sinks left over from computer parts. I also have tons of fans ranging in size so I don't think it'll be too hard to keep cool.
What do you mean make 2?

------------------
, Jon (350 TBI!)
91 Red My website

 

I think he means that you need to have a spare already made up ,in case it dies like the theory of always having a spare ECM ready. Dave

 

dp

[This message has been edited by JPrevost (edited October 23, 2001).]

 

I was just thinking about a few posts about how the stock ecms were designed to control injectors. I was looking at some other post and it said that the edelbrock EFI kit is just tapped into the stock wiring harness.
So if the GM ecms can control either 8 saturated injectors (high impedance) or 2 peak and hold (low impedance ~1.2Ohm), why can't a TBI system use a TPI speed density ecm? This would give faster data stream rates and the ability to go with an eeprom yes/no?!!
Grumpy, your input would be appreciated....again...lol

------------------
, Jon (350 TBI!)
91 Red My website

 

I wonder if the 8 injectors Edelbrock uses are P+H injectors or saturated injectors??? I heard that TPI/MPFI injectors can be either??????? From a Grumpy post I heard that, I believe???

 

P+H injectors run most effectively at 1-5 ms Pulse widths. Saturated at 2-10 ms. The TBI injector firing strategy fires the injectors alot more often, which means SHORT PWs. Ooops Saturated don't like short pulse widths.

The edlebrock uses saturated injectors. They just basically mess with the AE stuff in their chip. The improvement from TBI to TPI is substancial in THAT application, so people are rather easily statisfied. But, to get it correct takes a ton of work.

I have run a TBI of a TPI ecm, used the 8D code. Trouble was that while it ran OK, it was going to take alot of work to get really right. I burnt a couple dozen chips, and it just seemed like I really wasn't getting anywhere.

Seems like alot of folks are focusing on ALDL rates, which aren't that big of deal.

 

So Grumpy, are you saying that the Edelbrock PROM is messed with to change the output of the drivers so that the saturated injectors can live with the P+H drivers? Are the ms of the drivers changed for saturated injector use? like maybe BPW changes to make lonfer pulse widths for saturated use???

Ie, what did/do you mean by "change the AE stuff"

[This message has been edited by fast_broker (edited October 24, 2001).]

 

So the TPI will fire 2-10ms PW....from your information. And the TBI injectors like 1-5ms....so I don't see the problem. If you increase the BPW in the TPI prom, then you can increase the firing rate yes?
I'm going to take a look at the injector drivers on some TPI ecms. Hopefully I can dig up some important information and compare them to the TBI drivers.
What is the max and min PW in a GM ecm?
I ask because couldn't you just crank the fuel pressure and raise the BPW to like >200?
Or is there a max and min injector PW 'wall' that I would hit when running in PE or upper rpms.

------------------
, Jon (350 TBI!)
91 Red My website

 

Does anybody know the pulse width limits?

 

Geesh,
8 saturated drivers behave like 2 TBI injectors as far as LOAD.
I said effective operating ranges, iw where the injetor is happiest.
TPI is a dry manifold, so they don't need as much *acclerator pump* as a wet manifold does

 

Depends on injector size, and at what RPM your talking about.

 

65# inj at 5800rpm

------------------
, Jon (350 TBI!)
91 Red My website

 

I still wonder if the Edelbrock MPFI conversion uses (8) P+H or (8) Saturatd injectors. I just have to get on the phone to those guys. What is your oinion on this, grumpy? Are the P+H individual injectors common/cost effective for Edelbrock to use? Are all PICO injectors P+H or saturated, ie, is there a general rule???

 

ftp://ftp.diy-efi.org/incoming/External%20TBI%20P&H.jpg
What exactly is he pointing out? I found and notice the title at the bottom right, "quad driver."
Anybody know who posted this?

 

The edlebrock TPI conversion uses saturated injectors.

 

In EFI the are several parts to AE (yes, accleration enrichment).
The corrections are, and not limited to:
By delta TPS
delta MAP
Coolant temp.

Duration, and quantity

 

Last I heard the LM1949 was discontinued
Even the Cherry Semiconductor stuff is getting rare.
Beginning to look like some of the aftermarket co.s have cornered the market for what was left, on all fronts.

 

Sorry but no.
The TPI Peak and Holds are 2.4 ohms.
THe TBI Peak and Holds are 1.2 ohms.
But this will give you a P4 that will handle 2 TBI Peak and Holds.
Now if you look at the DIY archives you can find the pin outs changes to run 8D code in a 749. I do think you lose the TCC, but there are other answers for operating that.

 

I've been there and done the 4bbl thing. Unfortuantly I cant speak very technically on the subject but can speak as for how my system functioned.

I didn't read the whole thread so I'm not sure if it has been touched on but to make the 4bbl work on two TBI injector drivers, they have to be wired in two sets of series... not parallel, not series-parallel, just two sets of plain old series.

I did not use an add on injector driver system. I did zero custom tuning on my own. I ran a mail-order chip from Howell-EFI for the 1227747 ECM. As a mail order chip, it was less than perfect and I had some low end problems at first that were due to a bad injector. After the injector was replaced, idle and drivability were on par with a carb... (even with 10-11" of idle vacuum) as should be expected from a mail order chip.

Power? Great all the way up to 6k rpm (70's smog heads, performer intake, 219/227 roller cam holley 700cfm 4bbl with 65# injectors...in a 360ci motor). Ran 79mph in the 1/8th at 4500 feet... never got a good 1/4 mile time out of it due to a drivetrain vibration that was causing knock retard at about 80mph. So at 3600 pounds, (in bench racing mode now) the calculator says 265 rwhp here or over 350 hp corrected at the crank.

There has been plenty of theory tossed around and even some legitimate bench testing siting problems with 4 TBI injectors on two drivers... I can however say that my system worked even without custom tuning.

 

There is a huge difference from works to works correctly.
Some guys even have some really weird stuff run well, but that is the exception rather then the rule.
With the injectors you have you could be supporting well over 500 HP (fuel wise). It would seem at a glance that things are at least a little odd in that repect.

The series parrarel comment was in refernce to running 4 brl off of a 730 not 747.

I have no doubt you happy with your setup, but to infer that it's a proper answer is misleading, IMO.

 

Actually... although I know that neither you nor I am a great fan of holley... they rate that TBI unit for their kits to 400hp... the TBI unit with 85# injectors is the one they rate to 500hp. Yes, of course I know how to do the math to calculate estimated hp injectors can support... when drop the flow down because of maximum duty cycle and consider these are holley injectors that work well in the 10-17 psi range, you will realize they are in fact the correct size for a 350-400 hp application.

Wasnt trying to start a wee-wee match there grump... just wanted to let people know it worked, if you think its wrong thats fine, you are probably right but it did work on my car fully to my expectations.

 

Wasn't starting one.
just pointing things out.
Dunno but I consider guestions, and postings at formums etc as public information centers, and those asking a guestion are just the few that have the same guestion as many, so I tend to look at things as generally educational, where as most folks look at things as being a *personal* matter.
Oh well, please some of the people some of the time yada yada.
BTW, happy that your enjoying your EFI