V8 Astro TBI

[falconvan]

Hi all,

I'm new to the forum and still kind of a newbie to FI. I've done a few FI swaps but don't know much on the programming side or making changes from factory settings.

I recently put together a small V8 for my 86 Astrovan. I re-ringed a 68 307 shortblock, added a set of 305 HO heads and a TBI intake. Exhaust is stock manifolds with a 2.5 x 2.5 crossover going into a 3" single all the way out the back with a 3" turbo muffler and no cat. This is the cam I used:
Chevy 283,325,350,400 Cid Small Block Chevy Hydraulic camshaft,
1500-4000 RPM Range,
278 intake/288 exhaust Adv Dur,
Duration @.050 204 intake/214 exhaust,
Valve lift 420 intake/443 exhaust,
Lobe C/L 112

For the FI, I used everything stock off the 4.3. Throttle body, injectors, and ECM are all stock to the van.
It actually runs pretty decent with no check engine light on which surprised me. I does seems to idle low once the engine is warm; about 600 rpm. I'm thinking also with the extra cubic inches and more aggressive cam, I'm probably running lean once I hit highway speeds. My thoughts were to change the injectors to the larger 350 TBI ones and swap to the 87 and up model 1227747 ECM with a performance chip programmed to take advantage of the cam profile. I heard that the 86 model ECMs are too old and shouldn't be used. Any thoughts on the best route to take?

[dave w]

I think the 1227747 ECM is a good TBI computer with good aftermarket support. I think there is a HUGE difference between a "Performance Chip" and "Tuned Chip". For a modified engine like you have, I favor a "Tuned Chip". You can "Tune" a chip for yourself with TunerPro RT software. There are several options for programming chips, one possible option is to convert the 1227747 to a "Flash Chip". Here is a link to a post I did on converting the 1227747 to a "Flash Chip" :http://www.gearhead-efi.com/Fuel-Inj...-%2827SF512%29

dave w

[falconvan]

Wow, that's really inexpensive. Can you do things like remove the EGR functions by going this route, too?

[dave w]

Wow, that's really inexpensive. Can you do things like remove the EGR functions by going this route, too?

You will have "Full Throttle Access" change any chip parameter you WANT ... you are the programmer!

dave w

[falconvan]

You will have "Full Throttle Access" change any chip parameter you WANT ... you are the programmer!

dave w

Sounds cool; I'm sold.

[Six_Shooter]

First thing you will need to do is get an 8 cylinder CALPAK (the little removable chip under the access cover on the ECM) and program an EEPROM for 8 cylinder mode or find one. Right now, your ECM things that the engine RPM is a little higher (about 33% higher) than it really is, due to the 8 cylinder running on 6 cylinder programming of the ECM. It may be easier to just buy a complete ECM that is KNOWN to be from an 8 cylinder application, than finding just the CALPAK on it's own.
Both chips/ICs need to be changed in pairs, otherwise you get a cylinder count discrepancy and a CEL to go along with it.

Without setting the ECM to 8 cyl, the RPM dependent items will not trigger at the correct times, and can be difficult to tune around.

Going to larger injectors will definitely help. You can make yours adjustable, but then knowing the flow rate will be a guess at best, but is a budget way to increase injector flow.