CYLINDER AIR drops dramaticly at WOT

[RML_s13]

im having this trouble with this truck, but first thing first, i disable all torque management, increase spark and the truck stilll hard to do a burnout, if i touch the brakes just spins tires till 2k rpm, and with a dead spot cant go burning tires also, feels like no power at all in low rpms, im getting crazy with this truck, then at the track the cylinder airmass drops dramaticly and the spark goes so high and took of the gas, i really apreaciate your help guys, i want to learn.

Thanks for any help you could give to me

silverado 1998 jose angel TUNE 2.hpt
siverado banca vacio.hpl

[lukearmstrong1990]

your MAF HZ starts reducing from 3100rpm.

looks to me like you have a big restriction between your air filter and TB as can be seen with falling MAP value with RPM increase at 100% throttle.

restriction could well be your airfilter

unless you have a vac referenced fuel reg your Injector flow rates are wrong. the should taper up. take your stock IFR table and multiply entire table by the required value to make the 0KPA colum equal to your injector size. if you have a vac referenced reg ignore this part

[doctorbigblock]

don't forget restriction could be in exhaust also. do you still have cats?

[lukearmstrong1990]

I would have thought an exhaust restriction would struggle to build up a vacuum within the intake pipe/system

but if it were to be exhaust restriced to the point it lost power and "calculated" cylinder aimass reduced it would do the same.

[RML_s13]

your MAF HZ starts reducing from 3100rpm.

looks to me like you have a big restriction between your air filter and TB as can be seen with falling MAP value with RPM increase at 100% throttle.

restriction could well be your airfilter

unless you have a vac referenced fuel reg your Injector flow rates are wrong. the should taper up. take your stock IFR table and multiply entire table by the required value to make the 0KPA colum equal to your injector size. if you have a vac referenced reg ignore this part

im using an nnbs intake in a 01, i use nnbs fuel rail and c5 corvette fuel filter because the rails was returnless, so how would me ny ifr?

can be cause the drop from a leak?

[RML_s13]

don't forget restriction could be in exhaust also. do you still have cats?

no cats, muffler at the middle of the truck

[lukearmstrong1990]

remove your airfilter and airbox lid.

go do a WOT pull and log MAF Hz and MAP from 2000rpm-6000rpm full throttle. do this with your intake pipe just after the MAF (on filter side not TB side) vented straight to atmosphere. ideally do this somewhere with minimal dust as your engine will have no airfilter for the pull.

if MAF Hz and MAP are identical in the pull to your posted log problem is elsewhere. if however MAP stays stable and MAF Hz climbs the whole pull in comparison the your intake is your problem

[RML_s13]

remove your airfilter and airbox lid.

go do a WOT pull and log MAF Hz and MAP from 2000rpm-6000rpm full throttle. do this with your intake pipe just after the MAF (on filter side not TB side) vented straight to atmosphere. ideally do this somewhere with minimal dust as your engine will have no airfilter for the pull.

if MAF Hz and MAP are identical in the pull to your posted log problem is elsewhere. if however MAP stays stable and MAF Hz climbs the whole pull in comparison the your intake is your problem

im running a redline cai, i will try without the air filter, so with that fuel rail returnless style and the fuel filter from corvette my IFR are good?

[lukearmstrong1990]

if your system is returnless then your IFR values should taper for vacuum. IFR not changing as it needs to will play havock with fueling and VE numbers which will upset airmass calcs.

reload your stock IFR values...

or if you cant get them

28.1502751027316 28.584310181408 29.204360293803 30.7544855747904 31.1265156422274 31.6225557321434 31.9945857995804 32.1806008332988 32.3666158670173 32.6766409232148 32.8626559569333 33.1106760018913 33.4827060693283 33.7307261142863 34.1027561817233 34.5367912603997 34.9708263390762

respectively from 0KPA (28lb/hr) to 80KPA (35lb/hr) just copy the number don't worry about beyond the decimal.

try that. the way it currently is with constant fuel pressure basically as you get closer to 0KPA vac (100KPA MAP) or full throttle the PCM doesn't know that it needs to reduce IFR value thus adding more fuel.

bigger IFR number less fuel smaller it is more fuel basically. so factory set up allows the PCM to remove and add fuel on auto pilot in reference to MAP with the scales IFR data. saves the PCM working so hard with MAF and MAP. half the job is done by IFR. to have it as one solid value you need a vac reference reg and return hose. then with solid data the fuel is added/removed on "autopilot" if you will be reducing or increasing base pressure. both achieve same result.

set yours back to factory

[doctorbigblock]

what about fuel pressure?

[lukearmstrong1990]

what about fuel pressure?

my mistake. I have made the assumption you have constant fuel pressure at the rails all the time. a failing pump or voltage drop can also cause your problems. run a line and gauge so you can confirm constant fuel pressure is present and not falling away causing your symptoms.

also the ifr data will vary depending on base pressure be it 42psi (3bar) or 58psi (4bar)

[RML_s13]

if your system is returnless then your IFR values should taper for vacuum. IFR not changing as it needs to will play havock with fueling and VE numbers which will upset airmass calcs.

reload your stock IFR values...

or if you cant get them

28.1502751027316 28.584310181408 29.204360293803 30.7544855747904 31.1265156422274 31.6225557321434 31.9945857995804 32.1806008332988 32.3666158670173 32.6766409232148 32.8626559569333 33.1106760018913 33.4827060693283 33.7307261142863 34.1027561817233 34.5367912603997 34.9708263390762

respectively from 0KPA (28lb/hr) to 80KPA (35lb/hr) just copy the number don't worry about beyond the decimal.

try that. the way it currently is with constant fuel pressure basically as you get closer to 0KPA vac (100KPA MAP) or full throttle the PCM doesn't know that it needs to reduce IFR value thus adding more fuel.

bigger IFR number less fuel smaller it is more fuel basically. so factory set up allows the PCM to remove and add fuel on auto pilot in reference to MAP with the scales IFR data. saves the PCM working so hard with MAF and MAP. half the job is done by IFR. to have it as one solid value you need a vac reference reg and return hose. then with solid data the fuel is added/removed on "autopilot" if you will be reducing or increasing base pressure. both achieve same result.

set yours back to factory

Thanks bro for the help, ill try this IFR and thats the factory IFR from the stock ECM, im still using stock injector from nbs.

[RML_s13]

what about fuel pressure?

ill attach a fuel pressure gauge to see how its working at part throttle and WOT

[lukearmstrong1990]

I'm confident a large portion of your problems are caused by your IFR table in combination with returnless system and current VE table values