I used this: http://www.wikihow.com/Calculate-Percentage-Increase 550 is a 30.9% increase over 380 32.7% increase over 370 Correct me. E
You just got the last step wrong, Because you want a percentage increase you find the percentage of the difference/initial initial=380 final=550, the difference is 550-380=170 170/380=44.7% If you wanted to decrease from 550 to 380 then the percentage would be 170/550=30.9% for 370: 550-370=180, 180/370=48.7%
I think 30% is closer than 45%, the 45% appears to be lean. I think you would adjust the K value by the dividing the old injector size by the new injector size. I thought the stock TT injector was 370 cc. adjustment = 370 / 550 adjustment = 0.672 In theory the 550 K value should be 0.672 of the 370 K value. As a percentage that would be 32.8% reduction of the 370 K value which you would probably round to 32% to stay on the rich side. This 32% reduction produces (1 - (1 x 0.32)) x 550 = 374. The 45% reduction produces (1 - (1 x 0.45)) x 550 = 302. On the nistune site in this thread they discuss adjusting the K value from 288 (stock 370 cc) to 193 (550 cc). 288 * (370/550) = 193
So I just realised from Andy's post and re-reading Chili's that the trim value is a negative percent, so a percent reduction of the duty, not a percent increase of a directly input flow rate (I'm not a tuner...) So Tas' and Andy's math is probably more relevant than mine.
So Chili just to clarify and repeat a little, this MIXTRIM setting is a very rough adjustment, and even getting this close will vary likely not result in a safe tune across your entire map. You either need to buy and install a wideband O2 sensor and road tune it, or Take it to a dyno to be professionally tuned, or If the original stock injector tune was good, remove the 555's and put the stockies back in.
Which is a wise move UNLESS you intended to turn the boost up over what you were running in the first place. Big injectors for big injectors sake achieves nothing positive. E
Tom My bad. Im not too sharp on mathematics as you can see. Andy You shouldnt really view a K value change the same as a Mixtrm change. K value is a correction factor under the influence of many other trim factors. Mxtrm is a simple global change of injector time in percentage. Iis kinda similar but not the same if that makes sense. E
The blind leading the blind....... Half a dozen posts about mathematical BS relating to percentages of injector sizes is a waste of time At best, this method of adjusting K value should only be used to get a car started if you have no access to injector specs. I have no personal experience with Microtech, but judging by other posts it adjust trim values as a percentage. If so, that's okay.... adjustment is adjustment, BUT, (I'm in agreement with tassuperkart on this one) there is NO direct correlation between Microtech percentages and injector K value numbers I refer to my previous post : Firstly, you CANNOT correctly adjust anything fuel related without using a wideband O2 sensor. There are quite a number of 550/555 injectors around now and they are all going to be different (Nismo yellow tops are reputed to flow 615) so to assume a 'one size fits all' mentality is putting an engine at risk I also agree with Chili in the fact that dyno operators want to charge 'brain surgeon' rates, BUT, the small outlay for a WB O2 setup is cheap insurance compared to an engine rebuild. (and, like all zed related tools.... you only purchase it ONCE, all the rest of the time you get to use it for free )
If that is the case then why does Nistune tell you to adjust the K constant (injection multiplier) to resize injectors before tuning? http://forum.nistune.com/viewtopic.php?t=431 The Microtech Mxtrm also appears to be an injection multiplier constant that offers a quick method of resizing injectors before tuning. I agree that once the car is running it must be tuned to suit the injectors. It has been stated at least half a dozen times already in this thread. As far as I am concerned all the talk about injector resizing was to get the car running so it can be tuned. If you cannot afford to pay someone to tune the car or buy the equipment required then put the stock injectors back in until you can.
You need to BYO dongle if you want him to do microtech. Dongle/cable/software package is about $130 from microtech.
If you want, Toshi can reverse engineer an ecu, find its tables and write a custom tune for it. was going to do this with a Legnum. Guys a freakin legend.
Great Idea!!! someone should have really suggested going to Toshi all the way back on comment 17 page 1.... Oh wait....
This thread is confusing to say the least, as 2 different people as describing similar but different issues. My 2 cents worth is buy a WBO2 set-up (even if you just use a tail-pipe clamp for the sensor). The satisfaction of fixing it yourself is well worth it alone. Why paid someone else to have all the fun of revving crap out of your motor & using 1 or more tanks of fuel you pay for? Just don't put your right foot down too heavy till you get a good base tune sorted.
