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Injector Duty Cycle

2K views 19 replies 6 participants last post by  AZFXSTB 
#1 ·
OK did a few WOT pulls today on the dyno and logged the pulls I was seeing 80-86% duty cycle up around 5800-6200 RPMs. This is a Stock TB with Stock Injectors and the AFR was not leaning out but my HP just flat lines (101/109) at that RPM. Am I at the point of needing larger Injectors and TB or is it the cam?..? Build specs are below in Sig. From what I can find searching it seams 80%+ Duty cycle is bad so what do the experts say??:unsure:
 
#2 ·
OK just my opinion
The injectors are a red herring, but still if it were me I would change to the SE 07 injector (4.35)
The heads are a bottle neck. The BBz heads are what they are, a budget very high quality street head, and work very well on mild 95" motors. This is a larger motor with pretty good pipes and compression.
I am not sure your redline will go up much (6200 is a point where some other mechanical limitations come into play) but with a head change and camshaft you could pick up at least 10/10 and also gain a lot of torque under the curve.
I am not a fan of the cam, it is a TW37 with wider lobe sep angle which reduces the overlap.
We all want power and torque. At 10.3 I would look at the HQ575 and at 10.8 the HQ600. Both will get the job done with a set of heads such as HQ, Deweys, GMR, RR, Bob Wright, Larrys Machine, BC Gerolomy, T-Man, many others could get it done. The cams recomended by the porter would take precedence over the two HQ cams I listed but at 10.3 a 40° close and at 10.8 a 47° close work well, let them call the cam shots.
Want a little icing on the cake spend 600 or so for a larger TB (after the heads and cam) but just beware this will not get you all that much and the power will be top end only.
Big caveat
This combination will need to be tuned by a good tuner even with the Tmax I would run it after it self learns and play with timing and maybe some other AFRs
 
#3 ·
What I should do is shutup be happy and ride the bike because itruns GREAT but we all know that won't happen.:spank: well sounds like its a good thing I didnt get rid of all my take offs. So the 50mm SE TB would not be good..well there is another "extra" part. Also a 40deg close scares me at 10.3 here stock was 38 and it was pinging at 9.2...you gotta love this!drunk!
 
#5 ·
hdmarsh77 said:
I think I just read somewhere that once you hit 100% duty cycle, you maxed out the injector. In other words, you are ok. That is, if I remember correctly.
See to me that makes sense 100% is 100% but I also deal in the Networking computer world and once you his 75% throughput thats is considered "max" for reliable data:wacko: Im thinking that the fact that it did NOT lean out i would think im ok...just thinking out loud
 
#6 ·
AZFXSTB said:
What I should do is shutup be happy and ride the bike because itruns GREAT but we all know that won't happen.:spank: well sounds like its a good thing I didnt get rid of all my take offs. So the 50mm SE TB would not be good..well there is another "extra" part. Also a 40deg close scares me at 10.3 here stock was 38 and it was pinging at 9.2...you gotta love this!drunk!
I don't really pay all that much attention to CR numbers but the corrected number is much more important and either suggestions I gave will yield about 195 CCP which in Arizona may be a little touch and go. With the right quench (tight) advance curve and proper AFRs set it is manageable. This is the edge however and margin would be wise to allow for the days stuck in traffic in the AZ heat and from what I understand not very good gas.
The SE50 is not what it's cracked up to be but would be an improvement over stock and has the better injectors, are you running that now?
I would not even be looking at what the bike did stock and the claimed CR. Once the quench is corrected and the other tuning issues are dealt with the fuel requirements change. Many 07s had over .070 squish right from the MOCO so forget any data points there compounded by a overly lean EPA, even the stage 1, overly lean download.
Tmax new story.
 
#7 ·
nw_guy4_fun said:
I don't really pay all that much attention to CR numbers but the corrected number is much more important and either suggestions I gave will yield about 195 CCP which in Arizona may be a little touch and go. With the right quench (tight) advance curve and proper AFRs set it is manageable. This is the edge however and margin would be wise to allow for the days stuck in traffic in the AZ heat and from what I understand not very good gas.
The SE50 is not what it's cracked up to be but would be an improvement over stock and has the better injectors, are you running that now?
I would not even be looking at what the bike did stock and the claimed CR. Once the quench is corrected and the other tuning issues are dealt with the fuel requirements change. Many 07s had over .070 squish right from the MOCO so forget any data points there compounded by a overly lean EPA, even the stage 1, overly lean download.
Tmax new story.
I set the squish at .030 (zeroed the deck and used a .030 HG) Not running the SE TB yet but did order one for GP..right now with the 46deg my CCR is right at 178...just wish I could LEAVE IT ALONE..lol. I had a feeling the heads were the bottle neck for a 103 but I still feel like there is more in my setup
 
#8 ·
Well the TB won't hurt anything and may pick it up a few points and by using the bigger injectors the duty cycle will be less which reduces the cross port fuel robbing.
Have you messed with the timing on the dyno. This may be another source of hidden power. Also I know the cam has a 46 in close but the way they got that was by moving the LSA out and that robs the overlap. There are some good tuners in Phoenix that could help but I'm sure you know all the guys.
 
#9 ·
nw_guy4_fun said:
Well the TB won't hurt anything and may pick it up a few points and by using the bigger injectors the duty cycle will be less which reduces the cross port fuel robbing.
Have you messed with the timing on the dyno. This may be another source of hidden power. Also I know the cam has a 46 in close but the way they got that was by moving the LSA out and that robs the overlap. There are some good tuners in Phoenix that could help but I'm sure you know all the guys.
Have not done much with timing yet..I have advanced a little in the cruse range (just street tuning) but I just got the AFR were the engine seems to like all around. As to the Cam I really like it for manners it is VERY forgiving with detonation but knowing what I know now I may look for something with more overlap...how would the 575 be with stock springs?? If I remember right that is at the outside of max lift with the 06-08 heads and springs right?
 
#10 ·
AZFXSTB said:
Have not done much with timing yet..I have advanced a little in the cruse range (just street tuning) but I just got the AFR were the engine seems to like all around. As to the Cam I really like it for manners it is VERY forgiving with detonation but knowing what I know now I may look for something with more overlap...how would the 575 be with stock springs?? If I remember right that is at the outside of max lift with the 06-08 heads and springs right?
if you mean red shift 575 cams, zippers claims they bolt in to 06 and up heads
 
#13 ·
Totenkopf said:
just curious, who is tuning your motor?

The amount of ignition advance and the amount of fuel are interactive.
Me, yah I understand that but I wanted to get the AFR steady and offsets set before I mess with the timing. Tmax takes a while to get the fuel flow adjusted and if I mess with timing and the Flow changes alot I'm back a square one.#@SasF#
 
#14 ·
AZFXSTB said:
Have not done much with timing yet..I have advanced a little in the cruse range (just street tuning) but I just got the AFR were the engine seems to like all around. As to the Cam I really like it for manners it is VERY forgiving with detonation but knowing what I know now I may look for something with more overlap...how would the 575 be with stock springs?? If I remember right that is at the outside of max lift with the 06-08 heads and springs right?
Go to the HQ site, from their site
Special Note: All head Quarters cams with lifts below .650” will work in stock 2005-2007 heads with original equipment conical (beehive) springs, valves and seals. Performance head work is recommended but not required.

This cam with biased exhaust duration may help crutch the heads.

As far as the detonation you have a lot of safety margin now. If you wanted to keep that margin the HQ600 with 47° close is a sweet grind, in my personal 07 with a 107.

Tote is right about the tuning. Being on the lower side of the max compression a little more maximum advance may help pick up a few hp. Actually a leaner WOT may do the same, say something in the 13.2-13.5 range. What total advance are you running now?
 
#18 ·
nw_guy4_fun said:
Would have to be played with on the dyno. Could go either way slightly for an improvement. Also try the AFRs a little leaner if you are in the 12s at wot now.
It was in the mid 12s and the motor was loading up..Have it at 13.2 WOT now and it likes it much better....Funny thing is really with my setup I am chasing maybe 3-5 HP and TQ :whatever:
 
#19 ·
I've seen 1 or 2 degrees change in the spark advance make 5 more ft-lbs at the torque peak on just one change to the advance table.... and the only way to really know it is on a dyno, with someone that has tuned a lot of motors and they have a method of finding where the power is hiding.

Food for thought.

Otherwise you're just wandering around in the dark.
 
#20 ·
Totenkopf said:
I've seen 1 or 2 degrees change in the spark advance make 5 more ft-lbs at the torque peak on just one change to the advance table.... and the only way to really know it is on a dyno, with someone that has tuned a lot of motors and they have a method of finding where the power is hiding.

Food for thought.

Otherwise you're just wandering around in the dark.
I Like the dark:corn: Lol..I know what yah mean..Maybe in the next few weeks we will have to have a late night tuning party at my Fav local Indy and toss a few back and play with it..Nobody local really messes with the Tmax except me and TobeFrank
 
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