Cammed LS2 choking under throttle application cold since injector upgrade

[Jeffro88]

Hi guys im pretty new to efilive and a bit stumped with this one and so is my tuner. We fitted a new set of bosch 55lb injectors for an eflex setup to my hsv ls2 m6 running a 232/236 cam, 12:1 compression, fast 102 manifold, mafless, 4into1 long tube headers etc etc and ever since i have had an issue no matter if im on pulp98 or e85 where cold it will have like a choke effect under load and even after each gear change as soon as i touch the throttle. The symptoms happen worst when stone cold then seem to go away once it reaches around 75c degrees. Are there any extra tables that need modifying on an e40 when changing injectors? All he seems to have changed is an increase of the ve table and the injector flow base. I have attached a log and the tune file any help is greatly appreciated :)

[joecar]

The injector flow base table B4001 can't be right:

20307


If the max value is 8 g/s then the IFR and VE tables need to be scaled.

[joecar]

Are those injectors 55 lb/hr at 43.5 psi or at 58 psi...?

[joecar]

( and some of the other injector parameters don't seem right )

[joecar]

Is your FPR un-referenced...?

[Jeffro88]

Thanks for the quick reply joecar, the fpr is unreferenced, injectors are genuine bosch 52lb/hr at 43.5 or 550cc at 43.5, the max value for e40 is 7.999 so he modified the ve to compensate. He only modified the ifr and the ve table as this is the first e40 he has played with, therefore im guessing hes missed a bit. Ive noticed my calculations for the injectors are different to what he put into the ifr table but will this cause the issue? This is what my calculations for the injectors calculated out to:

MAP (kPa) Injector Flow (g/sec)
0 7.565598
5 7.612749
10 7.659610
15 7.706186
20 7.752482
25 7.798503
30 7.844254
35 7.889740
40 7.934966
45 7.979934
50 8.024651
55 8.069120
60 8.113346
65 8.157331
70 8.201081
75 8.244599
80 8.287888

Also i forgot to mention it has an intank walbro e85 pump but that shouldnt have any effect should it?

[joecar]

Ok, your tuner allowed the IFR table to peg from idle MAP (55-65 kPa) and up... he was hoping it would not have much effect...

he then proceeded to correct the VE using this IFR table, which for the most part most of the VE table will be a correct model...

( any small differences in his IFR and the calculated IFR will be taken care of in this VE table )

problem is what happens at the MAP boundary when the IFR is incorrect... idle airflow and VE produce different calculated airmass, so fueling will be different for each.



...
Ive noticed my calculations for the injectors are different to what he put into the ifr table but will this cause the issue? This is what my calculations for the injectors calculated out to:

MAP (kPa) Injector Flow (g/sec)
0 7.565598
5 7.612749
10 7.659610
15 7.706186
20 7.752482
25 7.798503
30 7.844254
35 7.889740
40 7.934966
45 7.979934
50 8.024651
55 8.069120
60 8.113346
65 8.157331
70 8.201081
75 8.244599
80 8.287888

Since table B4001 allows a maximum value of 8 g/s, the usual thing to do is to scale IFR, VE, MAF together by a factor X (say 0.75 or 0.5), and to shift left/down any tables referencing airmass (g or g/cyl) or airflow (g/s) on their axis (this can be time consuming since the shift is not linear);

or, the other thing that can be done (instead) is to multiply the IFR by X and divide B3601 Stoich AFR by X (i.e. making it leaner than it really is), this is much easier to do.

and now the VE table has to be re-corrected, but it will be a true model of your engine's cylinder airmass.



Also i forgot to mention it has an intank walbro e85 pump but that shouldnt have any effect should it?Not a problem as long as it can maintain rail pressure at 58 psi.

[statesman]

When you say 'your tuner', is he an actual tuner which you're paying to tune your engine or is it just a mate who's helping you out for free?

[Jeffro88]

Awesome thanks joecar i have booked in some dyno time at the end of the month to clean all this up and hopefully sort the issue out:thankyou2:
statesman - it is a good mate tuning it that has been tuning for years but this was the first e40 he had played with, he did the tune for me years ago after the fast 102 install and i was really happy with it so i gave him a shot with the 52lb injectors and eflex sensor. I was really happy with his tune again this time apart from the issues when cold

[joecar]

E40 is kind of like the LS1B.

[statesman]

statesman - it is a good mate tuning it that has been tuning for years but this was the first e40 he had played with, he did the tune for me years ago after the fast 102 install and i was really happy with it so i gave him a shot with the 52lb injectors and eflex sensor. I was really happy with his tune again this time apart from the issues when cold

Alright, I'll take a look at your tune file.

[Jeffro88]

Thanks statesman i think from the info from joecar about the maxed out ifr and the effect it has on the ve ive been set on the right track now, looking at b0200 in a comparison between my 52lb injector tune and the original ls2 injectors tune theres a whole section between 1200 and 2800rpm where he hasnt touched the ve from 60kpa through to 99.4kpa and it hits that area constantly in the logs when it plays up. Couple this with the b0110 and it explains why it gets better as it warms up. Hopefully im correct in my assumption that this is causing a massive lean spot lol

[statesman]

Alright, then I don't need to look at your tune file. :laugh:

[joecar]

lol......:cucumber::banana:

post your tune file.

[Jeffro88]

lol this thing has caused so much frustration its good to know i might finally be on the right track.
joecar here is the tune as is now and the previous standard injector tune

[Jeffro88]

Thanks for the help guys, had a day free to run it on the dyno over the weekend and found a heap of lean spots when the car is at cruising speeds and between gear changes. Fixed up the ve table and is finally fixed :banana:

[joecar]

Post your new ctz file, let us have a look.

[Jeffro88]

Here u go joecar