Dual TBI. Getting it to run

[dualtbi88]

I posted this originally in builds and restorations. I built it, now I need to tune this thing so I thought I'd post it here too to get some pointers. I left out some details from the other post to get more to the point. As of now I got a TPS high volt error. It idles high then slows down after the check engine light comes on. I plan on going with the EBL as soon as possible.







According to the Desk Top Dyno this thing should put out about 480hp.

I had a rough time getting it to run. I wanted to keep my truck TBI injected but didn't really know too much about tuning a speed density system. At first I went with the Victor II intake and a big block TBI and 90lb injectors.



After some reading I discovered I had nowhere near the air or fuel supply for this engine.
It's basically a hopped up ZZ4 GMPP engine. I installed Speed-Pro hyper pistons and a crane roller cam with 518 lift 286° duration with 112° lob separation.

I thought about different manifolds that had long runners and dual plenums. I wondered how cool would it be to have an old school look but run a modified stock EFI. After some searching I discovered the Offenhauser manifold. It had everything I was looking for. Long runners dual plenums and clearance for a stock hood. Now I just had to buy one.

To my amazement I found this on Ebay for just $211.00. The guy misspelled Offenhauser so nobody knew it existed. It was already setup for TBI injection with EGR modification.






I installed a scat crank, Pro Form Roller rockers, Clevite77 bearings, Melling High volume High flow pump, and Total Seal TS1 gapless rings. I bought a set of tall valve covers, polisjed timing cover, 7 quart pan and Ceramic covered headers from Ebay. Suprisingly the headers where really nice and fit prefectly. I did a little more fuel system upgrade as well. I went with AN fittings and added a Aeromotive fuel pressure regulator. It's a bypass unit so all I had to do was block off the old regulators and run the supply through a Tee to the TBI's, return back to the regulator, then to tank. I installed an FJO injector driver and walbro 255ltr per hour pump.




Now to get it together...




I fired it up and got everything working again. I'm about to send it to the muffler shop to get my 3 inch flowmasters welded up. Then I need to send my ECM off to Dynamic EFI.

I working to get it running for Cruising the Coast in Biloxi, Mississippi.

[1BadZ71Tahoe]

Great Build-Up.

Are you confident that you'll get the maximum amount of power from the Dual TBI's? Theoretically it will flow plenty, but can you get it dialed in tune-wise is the question.

I'm surprised you didn't give the P4 upgrade a try. You could have run that in SD or even the Hacked MAF Code. It would have required more tinkering, but a hell of a lot less than the EBL upgrade. WB02 readout can be integrated, along with Fan On/Off Temp Thresholds.

My all roller 305 w/ comp .496 lift cam and valvetrain kit (stock built bottom end minus flat tops), ported vortecs, edelbrock victor jr, and BB tbi I dynoed @ just under 240 with a base tune dialed in. I doubt you'll get 480 like the engine is built for, but you'll come close. ;-)

[dualtbi88]

What can I say. I have much to learn. What is the P4 upgrade? As of now if I try more than half throttle it really craps out. I'd love to really romp on the gas for once. I don't have any electronic tuning equipment.

[1BadZ71Tahoe]

I can't stress the following information: Definitely avoid the temptation to go WOT until you have the fuel and timing sorted out and are confident that everything is plenty rich to be safe. Too rich and you buy plugs and maybe an oil change. Too lean and you buy internal engine parts.

Ah, the P4 upgrade.

You'll have to search for all the information, but all it is, is running the updated 93-95 ecu that is still throttle body. 16197427 is the primary ecu used in these upgrades but there are a few others that have virtually the same characteristics. All you do is re-pin a few wires in the engine harness and hook this new forementioned ECU in. The computer has a lot more potential, and it's what everyone is hacking now-a-days. Faster processing speed is a major factor in this ECU too.

If your interested in learning more about the P4 search for "P4 Upgrade" and "16197427" at here and @ ThirdGen.org, but of course ask any questions and i'll help you out.

[1BadZ71Tahoe]

Buy a 16197427 Ecu.
Buy an ALDL Cable and Chip adapter and a couple chips from Moates.net. Oh yeah don't forget to buy a chip burner there too. Duh.
You download Tunerpro @ Tunerpro.net and MAF needs a MAF from a nbs vortec truck and a few other things.
You then need a BIN, and XDF file to match as close to your engine combo as possible.

Here's an excerpt from FAST305 about a base tune-in if your using SD with the 16197427:

In the P4 PCM, it is just injector flow and cylinder volume, NO BPWC calculations needed.

Next it is time to setup the timing table. For a mildy cammed engine I typically setup the distributor at 6* advance and set the corresponding initial timing setting in the ECM at 6*. This allows for quicker starting with a cold engine but does not put excessive drag on the starter at other times. The initial timing on the distributor and in the PROM MUST match or it will mess with the whole timing advance curve.

I then like to 0 out the PE tables, for simplicity.

I then take and setup the timing table. You have to be careful here as there are often BIASES applied to the tables. The ECM will not work with negative numbers as the hexdecimal setup will not permit it. Some OEM timing tables will actually go into negative advance at WOT and very low RPMs. To do this they apply a 9.81* (10*)bias to the timing. Then they will put 5* in the table perhaps. The end result is a spark reading of 5*-10 or -5* timing.

This timing table is not displayed with any biases (corrected for in the .ECU file) and is indicative of my Dart headed 355. It is actually an Iron Head LT1 map with slight changes due to the weight of the van.

When the timing map is complete we will work with the fuel map. Chances are the cam change has made the engine run very poorly, possibly even not run. The problem is in the fuel MAP. A stock L03/L05 idles at around 40 KPA or atleast 18 in/hg of vacuum. A cammed engine will idle at 50-70 MAP or roughly 14-16 in/hg. The loss of engine vacuum will give a rise in the MAP reading. The higher MAP reading is then sent onto the lookup table, where the ECM calculates the fuel injected off of the now incorrect cell. The ECM will be using numbers that would be indicative of a stock engine under load, while the modified engine is trying to idle. The result is much increased fuel delivery. At the same time the low-speed volumetric efficiency of the engine is killed off somewhat. This further richens the calibration. Then throw in the poor burn caused by the overly rich air/fuel mixture and things go down hill fast. The more duration, the bigger the problem, and the longer it takes to correct. Luckily the LT4 cam makes LOTS of vacuum at idle and should need only slight tweaks in idle fueling.

At this point I would set the PE/WOT Air/Fuel (A/F) ratio to around 12.5:1, this will ensure things are plenty rich, even if you make some mistakes in the VE tables.

I would change the Throttle Position (TPS) for Power Enrichment (PE spark/fuel mode) up to around 65-70% from whatever it is stock. This will allow you to see what is going on at higher loads and RPMs. I would not do this for long periods of time or hold the throttle right on the ragged edge of PE for too long though.

As you work with the calibration make gradual changes, this will allow you to see what is going on.

Some other tables of interest are the:

Idles Speed vs. Coolant-this controls the idle speed the ECM will attempt to run the engine at. It will need to visited when you cam a TBI engine. The stock TBI engines are happy at 500 RPM. Most cammed engines like 650-750 rpm for idle. I have also found that 700 RPM on stockish engines helps A/C operation on the hottest days (especially with a belt driven clutch fan), engine cooling, flat-tappet camshaft lubrication, and idle smoothness. Keep in mind that there are likely multiple entries for this. Idle in Park/Neutral. Idle in Drive/Reverse. Idle adders for A/C and the like.

Transmission Torque Converter Clutch parameters, properly setup they give a huge difference in driveability to even stock engines. The stock GM TCC strategy is all about Corporate Average Fuel Economy (CAFÉ). It SUCKS compared to what you can do on your own. Shift strategies on TBI trucks with the 4L60E are just as bad. Come on 3,800 RPM WOT shifts, I don’t know what GM was thinking???

Definitely avoid the temptation to go WOT until you have the fuel and timing sorted out and are confident that everything is plenty rich to be safe. Too rich and you buy plugs and maybe an oil change. Too lean and you buy internal engine parts.

Another good thing to do at this point is adjust the minimum idle air rate screw on the front driverside of the TBI. You should set this so that you Idle Air Count (IAC on a datalog) is about 5-10 steps on a fully warmed up engine in park/neutral with the A/C off. Too much IAC opening is actually bad, as it is an ECM controlled vacuum leak.

Now for the fun part!!! If you have a chance to get a 4L60E transmission with the 305/350 Vortec engine, it works awesome when used with the $0D code. I absolutely love my 4L60E. Here is why, consistent and controllable shift points all day long. (6,100 RPM @ WOT 1-2, 2-3)

You could search for all of this, but i'm a nice guy. hah.

[RednckChevy]

well when you get all of it squared away you wanna do the same fro my truck..i'll pay in beer...lol

[1BadZ71Tahoe]

Other points of interest:

$0d is going to be mentioned when your looking for P4 upgrade information. This is called the mask.

Your going to have to disable the 4l60e in the code because that's what came with the 7427 primarily. It's as easy as un-checking a constant. Then you'll be set to go with the 700r4.

A user that has the wording V8S10 in his username has posted the newest 0d XDF and BIN here on FSC somewhere, and i think it's on Moates.Net FTP server too. It's called Advanced 0D v?.? (whatever the newest version is).

There are Constants, Scalars, and Tables that need to be adjusted in Tuner-Pro once you've loaded the BIN and XDF.

Constants are either on or off, Scalars can be changed on a scale (IE: anywhere between 2.2 to 20 of some unit for example Percent, PSI, Volts -- whatever your working with), and Tables are basically an Excel table filled with numbers corresponding to the comparison of multiple sensors (one is on the x axis, the other is on the y axis).

There's a lot to learn man, but it will be worth it, then me and my Bro will travel and check out the truck and maybe give you a hand. I'm always up to visit my bro's hometown (Baton Rouge).

Later!

[dualtbi88]

Well looks like having my truck ready for October 10th is out of the question. That sucks. There is waayyyy to much to do.

[dave w]

Nice work! If I were to do the same thing (Dual TBI's) I would use the EBL ECM, if I was going to use a 700R4 automatic transmission. The EBL system can be modified to correctly operate Dual TBI injectors, by having the injector driver electronics modified. The EBL system with the "What's Up Display" and software are beginning tuner friendly. Keep in mind that tuning a dual tbi system is not tuner friendly, even to an experienced tuner.

dave w

[dualtbi88]

As of now I'm running an injector driver and the IAC's are in parallel. I'm using one TPS. I don't see tuning this any different than with having two VERY large injectors. It's all about air, fuel, and spark timing.
The big question what is easier to tune EBL with tuner pro or the P4 upgrade with burning swaping chips. These local salvage yard idiots want an arm and a leg for ECM's like they're made of gold or something.

I'm weighing time and money here. What is the cost of the P4 upgrade vrs the EBL and what is the learning curve between the two. I don't mind spending the money to save some time.

I have been a carborator guy for way too long. I have no issues tuning carbs and setting timing curves withsprings and weights. This EFI tuning is very new to me.

There was a fuel leak and engine fire that toasted my TPS wires while I was just getting it together. I may have crossed a couple of wires that's causing the high volt code. I'll cut into it tonight to see.

[dave w]

With the EBL system, there is nothing else to buy. With the EBL system, the data logging software and EFI tuning software is included in the system. The EBL system is a Flash system, which means no chip swapping or chip burning equipment is needed. The only advantage I see to a P4 is the ability to use a 4L60E or 4L80E automatic transmission. With the EBL system the use of a 4L60E or 4L80E is possible but requies using both a P4 computer and an EBL computer. The only draw back I see with the EBL would be in the rare event you need a replacement computer, a local parts store will NOT have an EBL computer on the shelf ready to plug-n-play.

dave w

[dualtbi88]

The Crane roller cam I'm using is a dual patturn cam for LT1's. it has slightly less lift and duration on intake vs exhaust. Makes for better idle and strong vacuum. I've got my regulator low pressure spring maxed out. It idles a little rich but accelerates a little better even at around half throttle every little bit helps. I connected the vacuum reference and that made a big inprovement before I maxed the fuel pressure. I'm thinking of swaping to the high pressure spring to see what happens. This engine was always a very thirsty mouse. I had the biggest accelerator pump I could get on my holley just so when I snapped the throttle it wouldn't bog. Though that 650 double pumper was chocking it bad, it still ran 12 flat in a Fiero on street radials and 3.31:1 gears . The car weighed a little more than 2800lb. I smashed a lot of trannies and custom built clutches. I temporarilly retired the fiero untill I finish the truck.

My truck should weigh about 3800lb with the stuff I cut out. It weighed exactly 4000lbs before the engine swap. I got rid of the heavy steel serpentine drive and built my own aluminum one. I replaced the cast iron heads with aluminum ZZ4 heads. The heavy stock exhaust is swapped out with a shorter lighter system. I also ditched the spare and and the mounting bracket. Replaced the bumper with a light wieght roll pan. I'll just have to see how it all subtracts from the total when I go to the scrap yard scale.

With a posi, sticky tires and better gears this truck should run in the low 13's upper 12's

[low4x4]

with all that hp and torque...your going to pull the vaccuum line right out of the brake booster and have no brakes.....i would make it flexible in the middle like the stock one....great set-up...good score on the intake....i have the ebl and it is easy to use...i did a mpfi conversion

[superlite]

dualtbi I haven't had a chance to call but will on wednesday if your not busy later on we can get meet up and pull some data if ya like,also I can get ya the comp you are looking for out of a 95 and no it isn't from my hoe.

[dave w]

Here is my post on a P4 upgrade. http://www.fullsizechevy.com/showthr...ht=%277747+RIP

dave w

[Six_Shooter]

No ECM modifications are needed in the later PCMs, to run all 4 injectors.

A friend of mine is using a '7060 which is very similar to the '7427 to run his 4 bbl TBI. It's a custom made throttle body using two GM throttle bodies. Been running that way for years.

You're on the right track, as far as the engine is concerned, it's just more fuel, it doesn't care if it's from 2 or 4 or 82 injectors, it's just fuel.

I bet that you have the ground and 5V reference wires crossed on the TPS, so it will show near 5V with the throttle closed, and around half a volt with the throttloe wide open. Your issue at half throttle would pretty much verify this. Do you have to hold the throttle open for it to start? That would be another indication, since anything above 4 or 4.5V goes into a "clear flood mode" at start up and shuts the injectors off. If you have the wires crossed in any other order, your guess is as good as mine how it would run then.

I am running a '7427 ECM in my Grandfather's '71 Chev truck, on a Corvette Crossfire system. Similar to yours, only two less bbls and two less injectors. lol

Due to some issues with the block of the last engine we had in the truck (starter issues) and a less than adequate fuel pump, we only just got it running well last night. We finally have good fuel pressure which has been the major issue all along.

Anyway...

I like the idea of the EBL, and I'm waiting for Bob to come out with the '7730/'7749 version, which may, although this is only speculation, work in the '7427 as well, I'll have to ask him. Anyway back to my point...
The EBL does have some great features, and would probably suit a first time tuner very well, due to what looks to be some intuitive displays, and GUI.

I tune using stock ECMs, and some equipment that allows me to tune in real time, much the way the EBL would, just using different equipment to do so, and without the extra inputs and outputs, that the EBL would provide, like e-fan, nitrous control and a few other things. There is some code floating around for e-fan control, for the '7427, which I plan to test out.

[dualtbi88]

low 4x4, I was reving my engine yesterday enough to make the truck rock side to side. I was concerned about the vac line situation when I first made the line. It does have some flex to it. I'm using urathane motor mounts from Energy Suspension so they are pretty solid. From what I can see the engine doesn't move much but that may change when I put a hard load at the drag strip. I'm looking into a better option for the line. I don't want to use an ugly hose. I may even do something similar as what I did to my fuel lines and use AN fittings.

Superlite, I'll be home tomorrow after 5:30. Your welcome to stop by anytime. Thanks for the help with the P4 ECM.

Dave, I guess I'm a sucker for a good challenge. What is the cost of everything I need to do the P4 upgrade. I do have a ALDL to USB cable. My darn laptop has a port error and I can't data log because of it. My computer genius friend is out of the country for a few weeks so I have no one to help me fix it for now.

P4 or EBL decisions decisions. lol.... I'm selling my 1995 Yukon SLE 2 door 4X4 so I can finish my truck. I may sell my 1998 Honda VFR800 as well.

[dualtbi88]

No ECM modifications are needed in the later PCMs, to run all 4 injectors.

A friend of mine is using a '7060 which is very similar to the '7427 to run his 4 bbl TBI. It's a custom made throttle body using two GM throttle bodies. Been running that way for years.

You're on the right track, as far as the engine is concerned, it's just more fuel, it doesn't care if it's from 2 or 4 or 82 injectors, it's just fuel.

I bet that you have the ground and 5V reference wires crossed on the TPS, so it will show near 5V with the throttle closed, and around half a volt with the throttloe wide open. Your issue at half throttle would pretty much verify this. Do you have to hold the throttle open for it to start? That would be another indication, since anything above 4 or 4.5V goes into a "clear flood mode" at start up and shuts the injectors off. If you have the wires crossed in any other order, your guess is as good as mine how it would run then.

I am running a '7427 ECM in my Grandfather's '71 Chev truck, on a Corvette Crossfire system. Similar to yours, only two less bbls and two less injectors. lol

Due to some issues with the block of the last engine we had in the truck (starter issues) and a less than adequate fuel pump, we only just got it running well last night. We finally have good fuel pressure which has been the major issue all along.

Anyway...

I like the idea of the EBL, and I'm waiting for Bob to come out with the '7730/'7749 version, which may, although this is only speculation, work in the '7427 as well, I'll have to ask him. Anyway back to my point...
The EBL does have some great features, and would probably suit a first time tuner very well, due to what looks to be some intuitive displays, and GUI.

I tune using stock ECMs, and some equipment that allows me to tune in real time, much the way the EBL would, just using different equipment to do so, and without the extra inputs and outputs, that the EBL would provide, like e-fan, nitrous control and a few other things. There is some code floating around for e-fan control, for the '7427, which I plan to test out.

So your saying the EBL can control E-fan, and nitrous? I do like the option of the 4L80E. My 700R4 was rebuilt and modified about 20k miles ago. I have a vette accumulator and a governer kit in it. I does pretty good for now. I may be lookin for an upgrade when it blows. I have an adjustable electronic fan control mounted to the radiator support. I made a fuse block for the fan control as well.

please excuse my ignorance... GUI?

[dave w]

Dave, I guess I'm a sucker for a good challenge. What is the cost of everything I need to do the P4 upgrade. I do have a ALDL to USB cable. My darn laptop has a port error and I can't data log because of it. My computer genius friend is out of the country for a few weeks so I have no one to help me fix it for now.

P4 or EBL decisions decisions. lol.... I'm selling my 1995 Yukon SLE 2 door 4X4 so I can finish my truck. I may sell my 1998 Honda VFR800 as well.

I use Datamaster data logging software: $119 http://www.ttspowersystems.com/DataMaster.html I'm good with Microsoft Excel spreadsheets, and knowing Microsoft Excel spreadsheets is an absolute must when using DataMaster to tune a P4! Datamaster offers a free trial version that lets you data log 20 times for free, then it's time to pay.

I use the Moates.net Burn2 Chip programmer to burn my chips: $85 http://www.moates.net/burn2-chip-pro....html?cPath=94

I use a PROM Chip adapter from Moates.net: $35 http://www.moates.net/g1-memory-adap....html?cPath=64

I use Flash EEPROM's from Moates.net: $5 http://www.moates.net/c2-sst-27sf512....html?cPath=26

I use freeware TunerPro software for chip programming: Free http://www.tunerpro.net/

In my area, I can get '427 PCM's for $50 ~ $60 when available.

So I think the total is about $300.

Just figure about 300 hours to learn and study tuning a P4 on top of that!
The P4 has two tables for fuel and spark, near idle and off idle.

dave w

[chevyz71man]

Yes the EBL can control nitrous and E-Fans.

I would personally run the EBL. If you ever decide to run a 4l60e or 4l80e you can piggy back a 7427 ECM to control it. Thats how my truck is and it works perfect. Just had a chip burned for new shift points and lockup.