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Old 05-05-2018, 03:04 PM
MethoD MethoD is offline
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Join Date: Mar 2016
Location: PA
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Default Want to change to direct-port -- initial questions

I want to tap my intake manifold (aluminum) for a direct port setup. Is it typical to tap it with the M8 tap and thread the injectors directly into the aluminum? Or would it be better to tap it to 1/8 NPT and then use the 1/8 NPT to M8 adapter plugs? Are there advantages/disadvantages to either?

I currently have nozzles in my intake piping post-intercooler. I would like to keep one there even after I switch to DP. But I can't decide what size nozzles to put where. I'd like to have an overall flow of about 1200 ~ 1300cc, but I don't know if it's better to have smaller DP jets and a larger post-intercooler jet, or the opposite. Again, can anyone speak to the advantages/disadvantages of either setup? (My engine is 4 cyl)

Is it better to put the DP nozzles as close to the head as possible? Because of my engine/engine-bay layout, the closer I get to the head, the less accessible they'll be for changing/cleaning/etc.

Oh, and finally, if I would tap the intake with the M8 tap, what size drill would I need to use? (inch)

Thanks
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Old 06-05-2018, 06:50 PM
rotrex rotrex is offline
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Join Date: Jan 2014
Location: Germany
Posts: 175
Default Re: Want to change to direct-port -- initial questions

Quote:
Originally Posted by MethoD View Post
I want to tap my intake manifold (aluminum) for a direct port setup. Is it typical to tap it with the M8 tap and thread the injectors directly into the aluminum? Or would it be better to tap it to 1/8 NPT and then use the 1/8 NPT to M8 adapter plugs? Are there advantages/disadvantages to either?

I currently have nozzles in my intake piping post-intercooler. I would like to keep one there even after I switch to DP. But I can't decide what size nozzles to put where. I'd like to have an overall flow of about 1200 ~ 1300cc, but I don't know if it's better to have smaller DP jets and a larger post-intercooler jet, or the opposite. Again, can anyone speak to the advantages/disadvantages of either setup? (My engine is 4 cyl)

Is it better to put the DP nozzles as close to the head as possible? Because of my engine/engine-bay layout, the closer I get to the head, the less accessible they'll be for changing/cleaning/etc.

Oh, and finally, if I would tap the intake with the M8 tap, what size drill would I need to use? (inch)

Thanks
If the aluminium is very thin, it is better to weld on a boss. It is very easy to cross thread the M8x0.75 thread with the jets in a thin plenum wall.

Core drill size is 7.2mm for M8x0.75

1/8 NTP is sealf sealing with some Teflon tape. Might be easier to tap and screw in.

Big central jet and small DP -> poor distribution, little advantages, if at all. You MIGHT get some air cooling, but you will mainly cool the piping and the intake manifold. Lots of puddling and removal of mist turning into streams of mix. These will pass straight though the engine into the exhaust.

Small jet and big DP jets -> best distribution and biggest effect. Least amount of charge dilution from cooling metal parts. Id even skip the post IC jet. Youll find it will have little to no effect compared to the DP jets.

You need the spray in the cylinder, so place them on top of the intake runners as close as possible and centered as possible to the injectors. Only this way you get a as homogenous distribution within the cyliner as with the fuel spray.

I always used deionized water and fuel cell grade methanol plus a filter. I opened up the jets after years of use and found nothing attached to the internal filter frit. Spray pattern was also as good as new.

Enjoy :-)
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