Hey Guys.... Well I want to really get started on this tuning thing badly, so I need to have a plan. I have been reading a little bit...... not enough yet, but as much as I get a chance to. I was reading up on how you can just repin the 727 (waterproof 730) to he able to handle a 2 bar Map sensor and run a $58 instead of buying the 749 ECM. But its not able to hanlde a certain type of injector (be it high Imp or Low imp, i dont remember exactly)

Which is the smarter way to go? Im expecting my D-1 Procharger tomorrow afternoon. Boosting about 7 psi. It will be more next summer. Whats the easier why to go? Whats the smarter way to go? Please help out a upcoming tuner

EDIT: I have a 1991 SD TPI Vette 6spd.... stock cept 1.6RRs no cats, MSD Digital6+, N.O.S.,..... and the Dual intercooled D1 Procharger, 7psi.....

 

Probably be best to stick with the '727; if that is what you are currently using. The '749/'730 use connectors that are quite a bit different then the ones the '727 uses.

RBob.

 

I was under the imprsession that the 727 was the same as the 730, just had a waterproof shell.....

So doin a ECM swap to a 749 would be undoable or what? What would I have to do to get it to work?

 

Repin your 727 to match SyTy wiring diagrams and load $58 mask into your eprom. So long as you use Sat(high) Z TPI injectors, it will work just fine.

 

Ok... So by doing this and throwing the 2 Bar map sensor on it will act as the 749 and be able to read boost?

I need new injetors anyways. Where could I go to find out what size I should go for. Do i have to do anything special for the new injectors to work? Im not sure but they come with High imp. already corrrect? So just basically going bigger.

How will my car run with just the basic $58 bin for 8 cyl and change the injector constant? Decent?? Will it run at all?

Im sorry for these stupid questions.... You guys must hate asnwering these questions over and over again, but Im having trouble finding info when someone is using a 727 ECM... All your guys help is greatly appreciated

BTW: (i dont know if this is aloud but) Does anyone have a $58 bin that I can play around with just to get a feel for it. I just want to mess around with it and see whats its like.

 

You'll want to to run the 58 code.
In going from the 749 to the 730 there are pin changes. I'm not sure how the 727 lines up with the pinout of a 749. I'd really suggest you fab up an ecm bench and work this all out ahead of time. You can run up to 57 PPH injectors, high impedance, and that covers up to about, about 850 HP.

Me, I'd relocate the ecm into the car, and run the 749.
With a plastic shell RFI is always going to be a worry, long wires act as an antennea.

 

some corrections additions.

727 uses a steel case.
Check out ludis lagens site he has a 730 to 727 pinout chart. by pin number.

I would never run a High impedence injector over 30 pph in a street driven car. I would go p/h.also the funny part is that running even a staurated injector Via p/h makes them act about 10% larger they have a longer useful pulse width. ill post up the data collected at lingenfelter running one of the Driver boards i have.

If you need a piece of hardware to run p/h injectors toss me an email. i have a few driver boards laying around from building honda hardware. they make a 727/730 p/h capable. i think i have enough parts to build 2.

on a side note if anybody needs a p/h driver board toss me an email ill be running a group buy pretty soon if theres enough interest.

 

This may be true but the vehicle doesn't. Do the '90-'03 Vette's still run a shielded ignition system as the older ones did?

RBob.

 

Considering the Syclones, and 86-87 GNs came with 29s, or 30s depending on the rating F/P seems like 30s aren't any big deal.
And the Syclones were a batch fire setup.

I believe Saturn 5 is running 30s in his 305.
Then there are some of the S/C 3800 guys running 30 PPH GN injectors in their cars.

And literally thousands of stock GNs running 36-40 and 42s.

With Lingenfelters ties to ACCEL, and them selling Driver Boxes, I can see where he'd favor using P+Hs.

The switch point for me, is when you wind up with too short of PW at idle for the saturated ones to work, which will vary by combination.

With the GN guys always updating, and with some clever shopping one (or more guys) can put together a set of cheap large injectors, and then find out where exactly where they are, before tieing the money up in set of new big injectors.

 

Vettes went to the CNP setup in 00 or there abouts.
But you knew that.

Add a MSD 6-7 or about any CDI ignition system to one, and when the ignition gremlins arrive, you can play all kinds of games looking for the problem. The stock HEI is marginally OK, since it's output is just below the really problemic level.

The Optynonsparks had their own issues, LOL.

 

Yes, brain fade, LS1's w/the CNP.

I've found the best upgrade for the HEI (even external coil small cap's) are a decent oil-filled canister coil. The mail-order house brand Made in USA's at $18US are a deal.

RBob.

 

So basically what you guys are saying I should do in short is...

Repin my 727 to the 749, run the 2 bar map, with a $58 bin, and 30pph High imp injectors.

What do I have to change to run the high imp. injectors? Do i have to do anything special, and is 30 going to be big enough?

 

Yup... 8 30 lb GN injectors.
No issues with them, passed Ohio E check with ease.

 

Repin your ECM to match a 90 Syclone/Typhoon.
No changes are needed as you already are running High Z injectors, changing to 30lb high z won't make a diffrerence as for as the ECM cares.


30's are good to around 500 HP... just watch your PW's and AFR.

30's seem to agree with a stock $58 bin.
You will also need to disable the EGR as the code does'nt convert the calcs well when switched to 8 cyl.

BW

 

Ok Very cool... That is what Im going to end up doing. Just have to find where i can get a diagram of what to repin where.

I dont have to worry about Emissions anyways.... So dont worry about that I was going to disable the EGR anyways.

I might think about acually going with 32s. Well see what happens. need to do a little more reading

 

https://www.thirdgen.org/techbb2/sho...t=749+diagrams

diagrams can be found on the diy-efi.org in the incoming folder.

 

Pinout for 730, 727, and 749

There are a couple charts there fir these three ECM's, just look around!

Have fun!

Edit: This is a better chart for what you want

 

36s or 40s would be my suggestion.
30s get a stock well tuned Syclone into the low 12s, just as a reference point.

 

I noticed that at 6000RPM I have a DC around 95 and as the RPMS increase it gets closer to 98 or so. This is with 42's and 47psi(vac off).

 

95%DC, is really the sign off point at 5K.

An interesting thing to do is build an ecm bench, and then spin it up driving an injector. As you get to 95%, at higher RPMs you can just listen to it start to chatter. There's not enough time for the pintle/disc/ball to fully shut off, so the injector gets erratic. During this phase of chattering and being erratic the fuel metering can go lean. Obviously not a good thing.

50s at an 80% DC would accurately flow what you have now.
Do you know what you idle PW is?. That would be the best guage of what injector you can best tolerate for a clean idle.

If you already know this, fine, but, maybe it helps stealdads67.

 

At around 850 to 900 RPM idle in P/N the PW is around .5 to 5. I thought about upping the FP a bit and trying that. I just bought the 42 lb injectors because I figured they would be more than enough.

 

Thanks guys this stuff is great...

Considering I have a TPI i never really go above about 5200 rpms

Im going to have to absorb all this in. I plan on building up the motor next summer. But for now the internals are stock. I think you guys are right though with the bigger injectors idea.

Just have to remember this is my daily driver, although i have another car just incase, I love driving the Vette and dont want to have it out of commision for to long because i cant gett he tune right, so before i start Im going to do as much research as possible and jsut use the FMU. by august I will prolly do the swap.

Should be fun.....

Thanks for all the help and support.


Edit, how much do your think is possible out of a well tuning supercharger 350 with stock internals? If I tune correctly, will that allow to to run more boost effecienly. Im going to start with a 8 psi pulley and hope i lose a pound or 2 through the intercoolers. i dont know what to expect out of it. What should I run or the power output... Should be fun to find out.

 

The Syclone guys can routinely break crankshafts with the 4.3s. Should be able to easily do that with an extra 30% cubes.

S/Cs and T/Cs are about boost. You want more HP, the dial up the boost. The talent is just seeing what boost level you can run and not break anything.

With boost the tension loads on the rods actually diminish, so rods are less likely to fail from tension loads then a N/A engine, so the next weak link gets to be the flange end of the crank. You might investigate the syclone stuff some.

 

Isn't the 4.3L Chev. V6 a split pin design; is that where the majority of crank breakage occurs?

 

Turns out the split pin cranks are better then the straight ones, usually. In the waning years of the v6 NASCAR Busch stuff, they were about all even fire engines. The better harmonics greatly offset the smaller in common journal area.

Most common failure I've seen has been the right at the rear flange. OTHER then detonation killing a journal.

 

Just a quick addition to the injector sizing portion of the thread, I'm running 36lb high imp injectors on a stock 305 with a blower and 749 code. No problems at all that weren't my own damn fault and she runs just fine. Haven't done much yet other than get the BPC set and dial in some of my BLM's. Got my romulator and a new aldl cable, now I just need to find time after work and women =)