gemellocattivo.com

Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
It is currently Thu Mar 28, 2024 9:52 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: Injectors!
PostPosted: Sat Nov 14, 2015 10:46 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
We did the high mount NA tests in late 2012. I was not part of them.

Based on the tests in early 2013 which I was around for, with the same injector and low-mount location, we were running rather high duty cycles (as high as 80% at 12k rpm). The 'low end' is from 5k-9k or so, so DC is much lower. At the time we weren't syncing to half cycle so there would be two injections per whole cycle 360deg apart. We increased fuel pressure from 3 bar (43 psig) to 4 bar (58 psig) to reduce DC enough to guarantee full injector closing.

With the low mount we weren't able to measure power differences with any change of injection phasing, because the injector DC was always really high.

With the high mount injector, the plenum did cool notably, and the runner was cold to the touch. It was a weird feeling.

With the turbo, we lose delta P on the injector as we add boost, and need more fuel flow to begin with, so two injectors were needed. No numbers on injector duty, I know it wasn't high enough to trigger any errors.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Sat Nov 14, 2015 11:03 am 
Offline

Joined: Sat Jan 03, 2015 10:13 pm
Posts: 794
Interesting post.

apalrd wrote:
With the turbo, we lose delta P on the injector as we add boost, and need more fuel flow to begin with, so two injectors were needed. No numbers on injector duty, I know it wasn't high enough to trigger any errors.


Not running a manifold-referenced regulator (or enough fuel pump to stack 4 bar on top of boost?)


Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Sat Nov 14, 2015 11:07 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
We used an in-tank pump with integrated regulator because it was lighter. We used to use the original WR450 bike pump but needed more flow and switched to one from a snowmobile.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Sat Nov 14, 2015 6:28 pm 
Online

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4251
apalrd wrote:
We did the high mount NA tests in late 2012. I was not part of them.

Based on the tests in early 2013 which I was around for, with the same injector and low-mount location, we were running rather high duty cycles (as high as 80% at 12k rpm). The 'low end' is from 5k-9k or so, so DC is much lower. At the time we weren't syncing to half cycle so there would be two injections per whole cycle 360deg apart. We increased fuel pressure from 3 bar (43 psig) to 4 bar (58 psig) to reduce DC enough to guarantee full injector closing.

With the low mount we weren't able to measure power differences with any change of injection phasing, because the injector DC was always really high.

With the high mount injector, the plenum did cool notably, and the runner was cold to the touch. It was a weird feeling.

With the turbo, we lose delta P on the injector as we add boost, and need more fuel flow to begin with, so two injectors were needed. No numbers on injector duty, I know it wasn't high enough to trigger any errors.


Its probably worth the effort to about triple your injector flow rate and repeat the testing. Try to hold the redline DC to under 35%...I haven't tried it yest but I'm told by people I trust that it's a few % hp bump once you have it right. With only 2 cylinders and your own injector test bench there's no really need to mess with the fancy dynamically match injectors but Injector dynamics does have a 2000cc injector that is probably just what the Doctor ordered if 700 :) (I have the 1000cc version)

Also on a boosted application you really do want to ref fuel pressure to the manifold. If you are running at a fixed bar and over 1 bar boost your injectors are seeing under 3 bar putting them outside their rated range and probably not spraying very well. Maybe just replace the spring on your in-tank pump and bump it to 5 or 6 bar if you don't want to mess with anything external? Or maybe plug the internal regulator and and use the ECU to manage pressure?


Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Sat Nov 14, 2015 9:29 pm 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
They're actually stock at 3 bar gauge pressure (NA). This engine is an I1 449cc for FSAE, the emissions engine is an I2 600cc.

We used to use the stock 3 bar pump/regulator but more power and E85 needed a lot more flow, so we switched from the stock injector to a higher flow Raptor injector and bumped the pressure up to 4 bar with that pump (plugged regulator and ECU control). Then, we went to a snowmobile pump which was already 4 bar. Then we added a bar of boost so we're back to 3 bar delta P, but with two injectors, and slightly more power.

I don't think any pressure increase will get 2 of these injectors to get down to 35% DC. For the upstream injectors, DC shouldn't matter since all of the fuel should evaporate before it goes into the engine.

We could go for 3, or a higher flow upstream injector, but the PW at idle (downstream only) is starting to creep up on the nonlinear region and we don't want to deal with that so we can't go bigger on the downstream injector.

The biggest issue with DC is that there is only 5ms per injection event at redline (two injections per cycle, no cam sensor), so there just isn't time for much working pulse width - the dead time becomes really significant. Even with 10ms the DC would only go.

Way back when we wrote the software the first time (and hit a DC limit with two pulses per whole cycle at 3 bar), we tried running sequential (But with no cam sensor still, so the half cycle was random) and didn't see any notable difference.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Sun Nov 15, 2015 7:29 am 
Online

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4251
ahh, you're still semi-sequential....the DI trick won't work that way as its very time (angle) dependent form everything I've seen. I'm pretty sure there is bit of fuel economy to be had with sequential but maybe not worth the effort.

Pressure --for some reason I just assumed you'd by over 1bar boost....no idea why I thought that. At 1 bar a 4bar fuel presure is perfectly fine as you clearly already knew.

As for non-linear, the ID injectors come with a full characterization...you just plug it in and go. nice.


Attachments:
Injector maps.JPG
Injector maps.JPG [ 290.39 KiB | Viewed 12399 times ]
Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Sun Nov 15, 2015 2:10 pm 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
We started with under a bar of boost since that's relatively safe for an unknown engine (with NO internal mods other than cams).

We're also restricted, with the restrictor pre-compressor (Restrictor->Compressor->Throttle->Engine) so as we start to make significant power, the compressor inlet pressure falls. Then, the compressor pressure ratio goes way higher than it should be for how much power we are making. A 1 bar of boost could easily push the compressor pratio to 3 or so, so making another bar (3 bar abs press/2 bar boost) would push pratio up to about 5-6.

With an I1, there is a very large exhaust pulse, and the exhaust runner to the turbo (about 1ft long of 1.625" tube) doesn't have enough volume to absorb the pulse, so it has to go through the turbine. This requires a larger than normal turbine to avoid restricting the engine. The turbine is also very happy with this pulse, and spools very quickly. The I2 saw similar behavior, both ended up with an MGT14 series turbo (from the Fiat Abarth 1.4L engine), and we did test several smaller turbos. We were able to swap a smaller compressor from the MGT12 family and this improved compressor efficiency but the compressor is still a bit large for the power we are making currently.

We have plans to improve all of this with more testing for the 2nd gen turbo powertrain.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
 Post subject: Re: Injectors!
PostPosted: Wed Nov 18, 2015 12:58 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
Pictures!

First, the WR450F injector (smaller one)

Second, the Raptor 700 injector (larger one) - The tip is identically shaped to the WR450F ones, but the body is longer. I didn't have any that weren't in something, so I took a picture in it's native place.


Attachments:
File comment: Raptor 700 Injector
IMG_20151117_223914160.jpg
IMG_20151117_223914160.jpg [ 924.24 KiB | Viewed 12392 times ]
File comment: WR450F injector
IMG_20151117_223800900.jpg
IMG_20151117_223800900.jpg [ 1.05 MiB | Viewed 12392 times ]

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke
Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 8 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group