TBI to Multiport Injection Conversion

[jmr302]

Has anyone installed one of these kits? Supposedly you can gain some hp and mpg with it plus it's just bitchin.

 

Edelbrock makes the kits.

P/N 3502 for 5.7L TBI truck engines '87-'92

P/N 3501 for '93-'95

P/N 3505 for 5.0L '87-'92

There's also an application for Vortech heads.

 

I stumbled across them in a Summit catalog and had never seen them before. You reuse your old throttlebody (injectors removed) and computer. Edelbrock / Summit.

 

Edelbrock claims a 4% gain in fuel mileage and 25hp/32ft-lbs at 4000 rpm on a totally stock engine. They claim bigger gains are possible if you add their cam, heads, and exhaust.

 

This kit looks great but it would be even better if the old Tuned Port Injection intake was used. That way you could generate another more low and mid range torque. There's no penalty to pay since these engines have such low red lines. If you look at a dyno curve on a TPI intake equipped engine you'll notice that there's no point in revving one past 5000 rpm. Seems like a good match to me. TPiS has found that the TPI intake adds 30 or 40 ft-lbs in the low and mid range compared to a carbureted engine (TBI has similar dyno curve to carb). The trade off is that a TPI intake runs out of breath in the high revs but that's fine for our truck motors.

 

Am I nuts? Has anyone here done a swap like this? Sorry for the long post.

[bassdog]

I thought about it jmr, but the cost is way too much for me. It does sound like a great system, but I have heard something about a computer swap or something to that effect, not sure.

 

Good luck

[jmr302]

Well that's the great part--you keep your stock computer. TBI only uses 2 injectors and really so does TPI. There are 8 individual injectors but they are batch fired one bank at a time so really there's only 2 injectors in the TPI system too.

 

I think the most valuable part in the Edelbrock kits is the adapter harness. That way you don't have to chop any of the truck's original harness. They also provide a new prom for the ECM but you'd have to burn a new one if you used a TPI intake. Maybe, just maybe it's possible to buy the adapter harness by itself. I'll pursue that when the time comes.

 

Stock TPI manifolds and parts should be pretty easy to come buy. If you shopped Ebay and some of the Corvette/Camaro forums you should be able to score a pretty good deal on that stuff. Most of that stuff gets replaced when people start modifying their cars. Fuel rails will probably be the most scarce item on the list because the most popular aftermarket TPI manifold reuses them.