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| Best angle of fuel injector nozzles? https://www.slantsix.org/forum/viewtopic.php?t=66394 |
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| Author: | MazdaRX8/6 [ Mon Jan 03, 2022 8:38 pm ] |
| Post subject: | Best angle of fuel injector nozzles? |
I have been looking at various fuel injection manifolds, and it seems most of them angle the injectors at about 45 degrees. One contributor here went to a lot of trouble to place his injectors at a lesser angle which involved notching the head and intake gasket slightly. Has anyone done research into which angle might be preferable? |
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| Author: | ProCycle [ Mon Jan 03, 2022 8:46 pm ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Ideally, you want to spray the fuel at the back side of the intake valves. 45 degrees doesn't do that but sprays the fuel at the bottom of the intake port. Our intake ports make a 120 degree turn. Apparently 45 degrees 'works' but it's not even half way around the intake port elbow. A better solution would be to put the injectors in the head so they can point the right way. That's a bit more work. Here's pics from a guy who did that. --> https://get.google.com/albumarchive/101 ... vqo-OG2nQE There are big compromises to make no matter how you slice it. |
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| Author: | MadScientistMatt [ Tue Jan 04, 2022 7:27 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
While 45 degrees isn't ideal, it's about as good as what a lot of OEM injectors manage. A less than optimal injector angle may need a bit more warmup and acceleration enrichment, but the differences are pretty tiny. |
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| Author: | ProCycle [ Tue Jan 04, 2022 7:49 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Quote: While 45 degrees isn't ideal, it's about as good as what a lot of OEM injectors manage. A less than optimal injector angle may need a bit more warmup and acceleration enrichment, but the differences are pretty tiny.
For most OEM engines 45 degrees is sufficient to aim at the intake valve. And the OEMs can design the injectors into the head rather than putting them into the manifold. On the slant 45 degrees only gets you part way there. 
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| Author: | MazdaRX8/6 [ Tue Jan 04, 2022 11:13 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Thanks for the replies. I'm not ambitious enough right now to put them in the head. Would it be safe to assume that the air flow would curve the spray and move it toward the intake valve? I'm using the Haltech ECU, and am having the seller tune it for me. I am not sure if the pulses are timed or not. I'll have to check. I'm using a Holly crank trigger wheel and a cam position sensor on the fuel pump lobe. |
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| Author: | MazdaRX8/6 [ Tue Jan 04, 2022 11:26 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Quote: Ideally, you want to spray the fuel at the back side of the intake valves. 45 degrees doesn't do that but sprays the fuel at the bottom of the intake port. Our intake ports make a 120 degree turn. Apparently 45 degrees 'works' but it's not even half way around the intake port elbow.
Looking at the cuttaway Procycle posted, there is water rigjt there in the head.A better solution would be to put the injectors in the head so they can point the right way. That's a bit more work. Here's pics from a guy who did that. --> https://get.google.com/albumarchive/101 ... vqo-OG2nQE There are big compromises to make no matter how you slice it. Procycle, looks like you went the extra step and increased the angle of attack for your injectors for your build. Was that based on science or gut? |
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| Author: | ProCycle [ Tue Jan 04, 2022 11:35 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Quote: Thanks for the replies. I'm not ambitious enough right now to put them in the head. Would it be safe to assume that the air flow would curve the spray and move it toward the intake valve? I'm using the Haltech ECU, and am having the seller tune it for me. I am not sure if the pulses are timed or not. I'll have to check. I'm using a Holly crank trigger wheel and a cam position sensor on the fuel pump lobe.
Will you be running a heated intake manifold with the stock exhaust? Or unheated and headers? With a cold intake manifold I'd expect some fuel to stick wet to the bottom of the intake runner. If the injection is sequential and timed with the intake stroke then airflow will certainly help move the fuel through. I agree that putting the injectors in the head is quite ambitious. I decided against it but if I was building another one I'd spend more time figuring out how to do it. It occurred to me just now that the injector bungs could be threaded into the head. Then the threads would only need to be sealed instead of relying on epoxy to hold them in place. I ended up using long nosed injectors and angling them down as far as was practical to get the fuel to squirt into the port instead of the intake runner. On the other hand I've seen Slant Sixes with the injectors spraying straight down. Presumably that worked OK and would be a lot easier to do the modification. |
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| Author: | ProCycle [ Tue Jan 04, 2022 11:35 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Quote: Quote: Ideally, you want to spray the fuel at the back side of the intake valves. 45 degrees doesn't do that but sprays the fuel at the bottom of the intake port. Our intake ports make a 120 degree turn. Apparently 45 degrees 'works' but it's not even half way around the intake port elbow.
Looking at the photos, if there is no water jacket in that part of the head it would seem really simple to drill the head for injectors. Does anyone know if there is water over there?A better solution would be to put the injectors in the head so they can point the right way. That's a bit more work. Here's pics from a guy who did that. --> https://get.google.com/albumarchive/101 ... vqo-OG2nQE There are big compromises to make no matter how you slice it. |
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| Author: | ProCycle [ Tue Jan 04, 2022 11:39 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
It can be seen in this photo Attachment: slant_z.JPG [ 76.08 KiB | Viewed 9168 times ] |
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| Author: | kesteb [ Tue Jan 04, 2022 5:03 pm ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
It really dosen't matter. The OEMs place the injector closer to the valve for idle quality and emission reasons. Placing the injector further up the intake runner improves atomization of the fuel. |
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| Author: | MazdaRX8/6 [ Tue Jan 04, 2022 8:40 pm ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Quote: Quote: Thanks for the replies. I'm not ambitious enough right now to put them in the head. Would it be safe to assume that the air flow would curve the spray and move it toward the intake valve? I'm using the Haltech ECU, and am having the seller tune it for me. I am not sure if the pulses are timed or not. I'll have to check. I'm using a Holly crank trigger wheel and a cam position sensor on the fuel pump lobe. With a cold intake manifold I'd expect some fuel to stick wet to the bottom of the intake runner. If the injection is sequential and timed with the intake stroke then airflow will certainly help move the fuel through. No manifold heat. I will likely use some form of the Gill Welding billet manifold. |
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| Author: | SlantSixDan [ Wed Jan 05, 2022 5:47 pm ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
For some views from Chrysler Engineering on the subject, see Figure 17 and the block of text below it on page 9 of this paper. |
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| Author: | Killer6 [ Mon Jan 10, 2022 6:04 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Without being able to open Dan's link on this phone, here are a few things to consider; While much cooler than the exh. valve, the intake valve is still much hotter than the port walls, enough to start to glow under extended/repeated full throttle games. Putting the spray on the backside of the valve does a number of beneficial things, not "just emissions". |
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| Author: | DadTruck [ Tue Jan 11, 2022 7:01 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Quote: If the injection is sequential and timed with the intake stroke then airflow will certainly help move the fuel through.
The statement above is true at low engine speeds, however with the engine at speed, the firing of a Sequential injector is not really different from a Batch fired injector. It is also mentioned in the article linked below that unless one is going to the time and expense of Dyno tuning the advantages of Sequential FI may not be achieved as to get to any advantage that Sequential injection has to offer, each injector needs to be optimized, you can't get there with a single O2 meter. https://www.diyautotune.com/support/faq ... injection/ A little off topic, but in the article that Dan posted a link to, the writing on page 3 and page 4 concerning the crankshaft material choices show an incredible level of transparency. I can guarantee that the company that I retired from would never admit in a public publication that a material chosen to go to production with, was chosen due to them being unable to figure out how to successfully process the material that was the initial first choice. |
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| Author: | Dart270 [ Tue Jan 11, 2022 8:16 am ] |
| Post subject: | Re: Best angle of fuel injector nozzles? |
Great perspectives here. Just to reiterate: Sequential will primarily give gains at low RPM and part throttle, and you will need to play with it a while before you find those gains, perhaps with a dyno. I am looking fwd to starting up my first sequential 225 engine and seeing what it feels/runs like... Lou |
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