Injector Pulse Width: Are these values too high?
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
Injector Pulse Width: Are these values too high? After reading a few threads, I decided to monitor my IPW's. I have quite a few 17's and 18's. My max figured logged so far is 18.33.
Now according to this...
https://ls1tech.com/ubb/cgi-bin/ulti...c&f=1&t=002558
...it indicates 18.33/20*100=91.65% duty rating, and that more than 80% is frowned upon.
Sooo...what's up with that? I'm also getting a slew of high 16's, and a full range of 17.x's. It's generally in the 3000-5500 RPM range, but doesn't happen consistently in that range. Does this go hand-in-hand with being really rich at WOT?
My car dynos around 400RWHP. I've heard of much more robust cars still using the stock injectors.
Do I need to be concerned?
Now according to this...
https://ls1tech.com/ubb/cgi-bin/ulti...c&f=1&t=002558
...it indicates 18.33/20*100=91.65% duty rating, and that more than 80% is frowned upon.
Sooo...what's up with that? I'm also getting a slew of high 16's, and a full range of 17.x's. It's generally in the 3000-5500 RPM range, but doesn't happen consistently in that range. Does this go hand-in-hand with being really rich at WOT?
My car dynos around 400RWHP. I've heard of much more robust cars still using the stock injectors.
Do I need to be concerned?
Teching In
Joined: Jan 2002
Posts: 30
Likes: 0
From: Wallyworld, CT
Re: Injector Pulse Width: Are these values too high? On my 1k mile new 02 TA (BONE STOCK) that's what I see with scan software. It was also my first thought (injectors close to maxed) <img src="gr_sad.gif" border="0">
Staging Lane
Joined: Jan 2002
Posts: 54
Likes: 0
From: Houston
Re: Injector Pulse Width: Are these values too high? Just wondering if the fuel pressure increases to meet the demand once the injectors are maxed out. I believe the max fuel pressure is 57 psi (4 atmospheres) although the injectors are rated at 43 psi (3 atm). Flow rate for 26 Lb/Hr injectors at 57 psi would be 26*SQRT(57/43)=30 Lb/Hr. Total theoretical horsepower at 90% duty cycle would be .9*30*8/.5= 432 Hp. This value of .5 Lb/Hp-Hr is for naturally aspirated engines.
There are some cars on this board that are making this at the rear wheels, possibly with 30 Lb/Hr injectors. Hard to believe stock 26 Lb injectors could be making this kind of horsepower <img src="images/icons/confused.gif" border="0">
There are some cars on this board that are making this at the rear wheels, possibly with 30 Lb/Hr injectors. Hard to believe stock 26 Lb injectors could be making this kind of horsepower <img src="images/icons/confused.gif" border="0">
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
Re: Injector Pulse Width: Are these values too high? The last time we monitored my fuel pressure on a dyno, it started at 59psi and fell to 56psi slightly past 4000RPM, when it started detonating bad presumably due to bad gas. Thus, we didn't see if it would've fallen further. I thought the stock injectors were 28.6lbs/hr, not 26? My car is a '98, maybe that's the difference.
On a further note, a more recent log gives me a bunch of IPW values in the mid-18's. But I'm a little relieved that I didn't implement the formula correctly. I wasn't changing the RPM value to match the log RPM. So, at least it's not happening as frequently as I thought before.
On a further note, a more recent log gives me a bunch of IPW values in the mid-18's. But I'm a little relieved that I didn't implement the formula correctly. I wasn't changing the RPM value to match the log RPM. So, at least it's not happening as frequently as I thought before.
On The Tree
Joined: Nov 2001
Posts: 108
Likes: 0
Re: Injector Pulse Width: Are these values too high? rpm dependant.
formula- 60000/rpm x 2 = max on time.
30 ms is 100% at 4000rpm
20 ms is 100% at 6000rpm
15 ms is 100% at 8000rpm
90% is fine for short bursts IMO. 95-100% should be ok for very short drag racing type use but you can run into problems with injector flow dropping way off at high duty cyles "just before they go static". Once static, flow is good but for to long and they can be damaged from the heat.
This is how I understand the situation with high duty cycles.
Steve
www.tech-ls1.com
formula- 60000/rpm x 2 = max on time.
30 ms is 100% at 4000rpm
20 ms is 100% at 6000rpm
15 ms is 100% at 8000rpm
90% is fine for short bursts IMO. 95-100% should be ok for very short drag racing type use but you can run into problems with injector flow dropping way off at high duty cyles "just before they go static". Once static, flow is good but for to long and they can be damaged from the heat.
This is how I understand the situation with high duty cycles.
Steve
www.tech-ls1.com
TECH Enthusiast
Joined: Nov 2001
Posts: 617
Likes: 0
From: Milford, Ohio
Re: Injector Pulse Width: Are these values too high? Above 90%, most pintle style injectors start to wildly fluctuate their actual flow rates independant of the pulse width. The spray pattern can also break down and fail to atomize the fuel spray properly. Plate style injectors (ie Lucas) are much more reliable at persistant high duty cycles.
Steve makes a good point about the max pulse width being variable based on RPM. Drop your 18.33ms pulse width back just 500 rpm and it becomes <85%, and at 5000 it's just 76%. Graph your pulse width against RPM and you'll get a better idea of how infrequently you're going beyond 90% duty cycle.
Steve makes a good point about the max pulse width being variable based on RPM. Drop your 18.33ms pulse width back just 500 rpm and it becomes <85%, and at 5000 it's just 76%. Graph your pulse width against RPM and you'll get a better idea of how infrequently you're going beyond 90% duty cycle.
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TECH Senior Member
Joined: Nov 2001
Posts: 10,341
Likes: 1
Re: Injector Pulse Width: Are these values too high? I think if your FP is dropping you need to look at increasing voltage to your pump or getting a new intank pump.
As for the PW issue I wouldnt worry about that so much. I have noticed that ATAP returns some funny numbers with the pulsewidth info. I think maintaining your FP is currently more important.
Cheers,
Chris
As for the PW issue I wouldnt worry about that so much. I have noticed that ATAP returns some funny numbers with the pulsewidth info. I think maintaining your FP is currently more important.
Cheers,
Chris
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TECH Resident
Joined: Jan 2002
Posts: 754
Likes: 0
From: USA
Re: Injector Pulse Width: Are these values too high? Here is a duty cycle chart that might help you
in knowing what you see in the PCM scans.
Duty Cycle Chart
in knowing what you see in the PCM scans.
Duty Cycle Chart
