Rb20 Flat Spot

[Psymon]

I've done a search and found a lot of results for flat spots but most of them related to RB25s.

At about 5000rpm my car seems to hit a huge flat spot, seems to get stuck there and doesn't want to rev any more. Mods are FMIC, Blitz panel filter, R33 Turbo, 3" turbo back, splitfire coil packs, remapped chip and 12psi boost. Spark plugs are BCPR6ES 0.8mm gap.

The only things i can come up with is the ecu might be going into a rich and retard mode similar to the RB25 ecu does or the spark plugs might need replacing. They've been in there for around 10,000kms now. Also could i have reached the limit of fuel pump (stock and original as far as i know), afm, injectors or something like that?

Also checked knock sensor plugs and they're fine.

Cold nights it's particularly bad. Once or twice in 1st gear its almost sounded/felt like a rev limiter at 5000rpm.

[zero'sR32]

ive never noticed any flat spot in mine... i have fmic, r33 turbo, 3"turbo back zorst at about 10psi... gonna tune it higher cause i got a piggy back and i wanna get gtr injectors... i already got a gtr fuel pump...

ill keep it in mind but...

[andylaurel]

its an RB20

the flat spot you are reffering to is the "lack of torque"

[Psymon]

Thank you for the most useful answer i have ever received on these forums. You really deserve an award and i'm proud to be part of a forum with members like you!

Yes it's an RB20, no the flat spot is not a lack of torque. The flat spot i refer to is something causing the engine to not perform to 100% of its ability at that particular point in the rev range, whether it be due to lack of spark, excess of fuel or something else!

Cold nights it's particularly bad. Once or twice in 1st gear its almost sounded/felt like a rev limiter at 5000rpm.

I didn't know a lack of torque could cause that!

The reason i asked was to get an answer that would help me fix my problem, not a smart ass answer that doesn't get me anywhere!

Edited October 21, 2006 by Psymon

[Gold_32]

Hey

I too have this problem and it is $hitting me to tears... It dosent feel like all the power is getting through at all. Im running front mount (justjap), 3" exhaust, pod, dump/front pipe and stock boost which is around 12psi with these mods.

In testing this against a mates car (sr20 n/a), its embarrasing to say that i am getting cleaned up in my rb20 r32... at least im not the only one in this boat it seems! good luck with finding the problem, if i find a solution i will pass it on.

[Psymon]

At the moment i think the most likely cause is spark plugs. I might grab a set tomorrow and see if that helps out at all.

[yogi000]

hey dude

have you tried doing an ecu diagnostic check

its fairly quick and easy

[Psymon]

I haven't tried that yet. The thought has crossed my mind a couple of times. Might try it after work today.

[1kool34]

Hey Psymon i had the same problem in my 32,but it was lower in the rev range, between 3500 to 4500 it was absolutely gutless. couldn't work out what it was until i bought another turbo, bang problem gone. I put my problem down to a stuffed wastegate actuator. Hopefully its not this in your case but like yogi000 said a diagnostic check hopefully will help you out. Good luck

[Cubes]

Could be a fuel pump on its way.

Throw it on the dyno for a power run to check out the afr's.

Shop around power runs can be had for as cheap as $30 from some places.

[123456]

For me it was a fuel pump, could really feel the engine dying at above 5k, for want of fuel. Bosch 044 fixed that, get a fuel pressure/flow analysis done at a mechanics, cost about $60

[Psymon]

Yeah i think it could be a fuel pump as well. I just ran diagnostics and the only code i got was 54 (auto signal) but the auto is long gone so that makes sense. I'll try the plugs because they're due to be changed anyway and if that doesn't work i might get the pump tested.

I think i saw some cheap 040's for sale!