Duty Cycle and Datamaster
Thread Starter
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Duty Cycle and Datamaster
What kind of Dutycycle numbers are you getting with your datamaster program? I was told that that number isn't all that accurate but mine are pretty high above 5000 rpms.
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
mine go over 100.. but i've been told that isnt as important as the how many ms the injector is open.. I've been told anything around 16-18ms is nearing the injector hanging wide open (bad).. I'm around 10-11ms max and I feel comfertable with that.. regardless of what the DC reads.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
78% max.
I don't know about how hard it is to tune bigger injectors on other motors but with the LTx it is prety simple and I like to keep my DC below 85-90% just to be on the safe side. I have 36's now and have run 42's with the same drivability so I know I could have gone bigger but why? If my DC's where around 60-70 I would have droped back down to 32's but the 36's put me right about where I wanted to be so I am sticking with them, would have liked 85% in a perfect world but life goes on.
I don't know about how hard it is to tune bigger injectors on other motors but with the LTx it is prety simple and I like to keep my DC below 85-90% just to be on the safe side. I have 36's now and have run 42's with the same drivability so I know I could have gone bigger but why? If my DC's where around 60-70 I would have droped back down to 32's but the 36's put me right about where I wanted to be so I am sticking with them, would have liked 85% in a perfect world but life goes on.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Originally Posted by FD2BLK
78% max.
If my DC's where around 60-70 I would have droped back down to 32's but the 36's put me right about where I wanted to be so I am sticking with them, would have liked 85% in a perfect world but life goes on.
If my DC's where around 60-70 I would have droped back down to 32's but the 36's put me right about where I wanted to be so I am sticking with them, would have liked 85% in a perfect world but life goes on.
Wise man...listen to him
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Wheren't 30's to big for all cars runing slower than 10 seconds?
The duty cycle calculations are skewed in datamaster. Duty cycle is not something you pull down from the ALDL stream but derive from injector PS and RPM.
I can't remeber the exact formula but I always remeber that around 20ms at 6000rpm is maxed out completely (hanging open) take 80% and you get a *properly* sized injector.. so what 16 ms at 6,000?
I don't worry about the *proper* / *improper* injector sizing routine.. I just tune until I see that linearly rising slope of death AFR line. I've found that 30's in most applications will do 430rwhp no problem in a NA car. I haven't maxed out a 36 NA but I would assume it would start falling at 480-500rwhp. And of course these stats are at a reasonable designed working pressure of 40-45psi.
This all depends on the car however.. My car is maxing 42's out at 480rwhp but its a blower car and requires more fuel per HP for cooling.
I have a few dyno sheets around left over from my car.. I can explain how I find when I have too little injector or not.. Let me gather them up and i'll post them.. I think it would be interesting for all to see
Last edited by Alvin; Sep 22, 2005 at 10:39 AM.
Thread Starter
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Originally Posted by Alvin
Alvin,
I am off to the dyno tomorrow, I am going to resend datalogs and dyno sheets to you. My DC on my datamaster program is approaching 130.
I just put a miniram on and still have my 22lbers. IYO do you think the 22's are still up to the task? I am going to have you change a few things on the chip too. I put a 190l pump in yesterday and filter so I am trying to eliminate problems before they arise.
Tom
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Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
To be honest, I really can't remeber your setup.
22's with a stock or near stock stall can take you up to 35xrwhp but in some cases they fall short at 330rwhp. With a good pump you should be able to do at least 350rwhp no problem (with a stock/near stock stall.. or high effecient one at least)
22's with a stock or near stock stall can take you up to 35xrwhp but in some cases they fall short at 330rwhp. With a good pump you should be able to do at least 350rwhp no problem (with a stock/near stock stall.. or high effecient one at least)
Thread Starter
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Originally Posted by Alvin
To be honest, I really can't remeber your setup.
22's with a stock or near stock stall can take you up to 35xrwhp but in some cases they fall short at 330rwhp. With a good pump you should be able to do at least 350rwhp no problem (with a stock/near stock stall.. or high effecient one at least)
22's with a stock or near stock stall can take you up to 35xrwhp but in some cases they fall short at 330rwhp. With a good pump you should be able to do at least 350rwhp no problem (with a stock/near stock stall.. or high effecient one at least)
I have a 219, tricks, tpis headers, 26-28 vig, and just replaced the big tubed runners. Now I have the mini with a 190litre pump.
Also is there a rev limiter in your chip?
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
You should be getting close but you won't be maxing it out yet. How do you like the chip so far?
I don't put a rev limitor in them unless people ask for them. The factory doesn't put them in in those years.
I don't put a rev limitor in them unless people ask for them. The factory doesn't put them in in those years.
Thread Starter
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Originally Posted by Alvin
You should be getting close but you won't be maxing it out yet. How do you like the chip so far?
I don't put a rev limitor in them unless people ask for them. The factory doesn't put them in in those years.
I don't put a rev limitor in them unless people ask for them. The factory doesn't put them in in those years.
I will let you know what happens tomorrow. So far I am pretty happy with the chip just would like to do a few tweaks.
I said I had that little surge, well it went away with the new intake.
Another thing with the new intake is I am getting a backfire 1 out of 25 times I go from low tps% to around 30-40%. Is that a tip-in issue due to the increased airflow from the intake?
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
Originally Posted by hippy
What kind of Dutycycle numbers are you getting with your datamaster program? I was told that that number isn't all that accurate but mine are pretty high above 5000 rpms.
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
Come on guys, quit guessing. There are a large number of resources online that will allow you accurately calculate injector sizes.
Assume 0.45 BFSC for a NA motor and use the calculator or the chart and quit guessing.
Now if you don't mind going lean and blowing a motor than keep guessing.
Perry
(Google for injector sizing)
Assume 0.45 BFSC for a NA motor and use the calculator or the chart and quit guessing.
Now if you don't mind going lean and blowing a motor than keep guessing.
Perry
(Google for injector sizing)