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Old 12-18-2012, 04:47 AM
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Type 2 vs Type 3 Injector

Can anyone explain the differences, other than physical dimension, between type 2 and type 3 injectors? Along with the differences maybe the pros and cons of each also?
I'm in need of a set for GM TPI setup and I'm unsure which to buy.

Any input is appreciated.

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Old 12-18-2012, 07:17 PM
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Quote:
Originally Posted by 64nailhead View Post
Can anyone explain the differences, other than physical dimension, between type 2 and type 3 injectors? Along with the differences maybe the pros and cons of each also?
I'm in need of a set for GM TPI setup and I'm unsure which to buy.

Any input is appreciated.
Big difference is spray pattern, the three delivers a better atomized pattern than the 2. It is reputed to last longer than the 2 as well. Aside for that the 3 and 2 are dimensionally interchangable.

Bogie
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Old 12-19-2012, 09:48 AM
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Quote:
Originally Posted by 64nailhead View Post
Can anyone explain the differences, other than physical dimension, between type 2 and type 3 injectors? Along with the differences maybe the pros and cons of each also?
I'm in need of a set for GM TPI setup and I'm unsure which to buy.

Any input is appreciated.
I looked into this same thing when I first got a L31 Vortec engine and was considering my options for fuel delivery. Evidence points to the 3 as being better overall.

What's also very important IMHO is to size them correctly. Then they can be fine tuned w/fuel pressure if needed. Just like w/camshafts and carbs, guys (not you personally) tend to go overboard thinking "more is better!" You do not necessarily want a higher flow unless it's actually needed, and too big can even hurt idle quality. My belief is there are a lot of engines with >/= 42# injectors that would run as good if not better with </= 30#. Even 24# can feed a fair amount of engine, but too small obviously isn't good either.

Good luck.
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Old 12-19-2012, 04:41 PM
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I spoke to South Bay Fuel Injectors yesterday and was told the same thing about the difference. In terms of sizing,I've read all kinds of contradictory information. I've found that when trying to explain my engine and the use of the vehicle that most people get tangled in WOT performance, but idle quality and cruising fuel economy is a major concern. Also, I've entered data into at least 10 different injector size calculators and the results are not the same. Basically, depending on the calculator I've found recommendations from 21 lb to 28 lb.
South Bay recommended type III with 27 lb and I think that's what I'm going to go with.

I'm open to all suggestions.

Engine is .030 327 with 6.25" Crower rods with .500 lift cam with 1.6 roller rockers, stock 69cc heads 1.94/1.60 with minor porting done. Compression is between 10.5 and 10.8. Wintertime project is conversion to TPI merely for fuel economy and idle quality, and of course tuneability. Also has 200 4R.
With 650 Holley on Holley dual plane it is plenty snotty enough. I know the TPI will run out air when much over 5000 rpm's, but it rarely runs in that range anyway and it runs out of HP at 5800 rpm's according to dyno tests. I think, repeat think, that the TPI will make the bottom end grunt a little better due to length of the runners. BUT, time will tell.
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Old 12-19-2012, 05:03 PM
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I like the idea of the 27 lb/hr units.
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