4AG'T'E Surging on the road and dyno - tune?

[mattysshop]

hi all, i'll give you a basic rundown on my mates setup..

S/T 20v head
GZE block 'unkown forged internal/rods'
custom big single TB plenum
ID 1000cc inj (was planning on E85)
GT2871 .64 rear, with machined tapered bung in internal wastegate port.
38mm external gate
i belive it's an 044 (or some large bosch) with a surge tank etc..
adaptronic e420c

so now the problem is it's surging... like when you accelerate hard to WOT it sorta boosts to 11-14-11-14-11... and seems to do it through out the rpm points...

*since the problem first occured, the Eboost was looked at... it was always resetting itself, and playing up even as it was setup correctly, it was sent back to turbosmart under warrenty - not sure what eventuated.

*then he ran a bleed valve... and it was doing the same thing..., so they got the Adaptronic controlling boost

*diagnosed the tial 38mm gate (also 2nd hand) may be a problem... brand new 38mm tial gate fitted... same problem

*somewhere along the line the map sensor shit it self and overfueled horribly...

so he is thinking that the cat might have melted.. 3" stainless magnaflow metal cat btw...


the guy that is tuning it i have never really heard of... apparantly he does alot of rotors, and circut racers... fair enough... (i'm not slagging him or the shop so it will remain nameless)

but i seriously think it's all in the tune, as he stated that once they had it up around 21psi at one stage and it was making a cracking 150hp at the wheels... i questioned the timing curve... but as i said i'm no tuner...

from what i have discussed with him the fuel system has been ruled out, due to the pump's being 'new'... but i'm not convinced that is a good enough reason..

thoughts?

[old_mr2]

Has the ex manifold been checked for leaks?

[mattysshop]

all the fabrication is brand new.. Extreme Custom Engineering ofcourse, as previously the setup was absolute rat shit...

only thing different from these pics, is that all the dump/wastegate pipe/manifold has been HPC'd silver, definitly no leaks...

[knightrous]

What are the AFR's like while it's surging?

[midnight_purple_GA70]

i am no expert but the distance those injectors are away from the ports lookst to be alot bigger than i would of thought...

this being said if boost is fluctuating/surging im not sure it would definitely be fuel related

is the solenoid for tha adaptronic working correctly? (not sure how they run their boost control)

routing for the wastegate vac hoses correct? assuming it hasnt been left as pictured?

[boxh34d]

At 21psi I would expect closer to 250hp at the wheels, not 150. . . . . .
Does it surge consistantly all the way to redline, or get better / worse at different rpm ranges or change with boost level? Does it pop / fart / bang / miss etc, or just surge in boost and then power accordingly?
GT30 something turbo . . . . Any more definative on size of comp wheels and exhaust AR etc? The turbo could be too big causing the thing to surge as the engine is looking for more air than the turbo can provide. The previous question may also help eliminate this one.
If its done it with both the bleed valve, and the adaptronic then I think the ECU boost control is irrelevant. Even if a bleed valve is used just to help with the fault finding.
Other things I can think off the top of my head:
Fuel pressure - just whack a temporary gauge on the rail somewhere to make sure its ok as stranger things have happened. Can you chuck up a dyno graph with power vs AFR and one of boost too. Should help determine if its hardware or tuning related.
1000cc injectors are awefully bloody big for a 1.6. Has the tuner mentioned anything about difficulty in maintaining AFR's with small injector opening time changes making a big difference etc?
What is the base timing and advance doing under boost?

[mattysshop]

i don't know if he has any sheets regarding the AFR's, but i'll ask him, i remember seeing a table of a timing vs boost not too long ago being discussed in a thread... can't remember exactly what it was though...

hopefully he will be able to get some info on this, cos i know it's frustrating him to no end!

[midnight_purple_GA70]

the jz tuning talk thread has lots of discussion about timing vs boost...

[mattysshop]

ok, his words -

"they've had everything apart. there thinking maybe the intake manifolds too big, or somthing to do with the turbo. Got the vvt working it's making 40% more torque and it's coming on boost at 4500 pulling like a train. but it's only revving to 6 before it starts surging."

"can't even notice it in 1st and 2nd.."

and he sent me a very ilegeble pic of a dyno print out - i can read between 155-160hp at the wheels... can't see any AFR's etc.. but i've asked him to scan the sheets he has.. so hopefully we will have something in the next few days for you tuners

GT2871 .64 rear, with machined tapered bung in internal wastegate port.

and that inlet manifold is not really that big... it's extremely well made inside with sunken/ported runners etc... injectors have been set up on the milling machine at the correct angles etc...

[SHEPPO3930]

what are the AFR's doing when it starts to surge?

how much timing is being used on boost? power is way too low for the amount of boost being run.

have you tried to put a smaller GT series turbo (like a GT2871R) on it and run similar boost? this leads me to my next question...

have people used this exact spec turbo on similar set ups before? the compressor v turbine sizes seem like they are are a little too mismatched and the set up may be suffering from compressor surging (turbo supplying more air than the engine can consume).

what valve ? stock springs can cause valve float when 20V ST's are boosted.

[mattysshop]

sorry i had the turbo wrong, it is GT2871 .64 rear, with machined tapered bung in internal wastegate port, brand new through MTQ,

it was a boosted engine before, from Sam Rigoli's green AE92... with all the shocking fabrication fixed (don't know how many hands it went through between rigoli, and my mate)

i would assume that if it didn't float at 1 bar before, why should it now?


the tuner seems to think the plenum is too big? and has tuned it on both sides of the lamba scale, makes 140hp without surging, and when it gets to 155 it goes crazy..

i'm double checking with him to see if it's due to timing increase, or boost increase that the surging happens..

[Bazda]

Thats a hard one to diagnose.

A good tuner would know from looking at the AFs, timing and by feel what could be causing the problem.
What plugs are you running?

And it also seems to be more apparent when its loaded up in the higher gears.

Possibly the spark is being blown out (try some protruded prong injectors) or a colder plug.

[thechuckster]

Some things on high rpm surging come to mind:

- what is dwell doing
- FPR, what make, hopefully not rising rate, where is reference for MAP connected
- correct driving of injectors at big PW
- AFRs, like the rest of the posts, this will help
- stable trigger at high rpm

[mattysshop]

Plugs are BCPR6ES gapped at .8, and they tried to close it up a little also... have gone through a few sets of these, and 3 sets of 'standard 20v plugs' new leads etc (not those ones pictured, another set)

FPR is a Malpassi rising rate - connected to the plenum via hose barb, the BOV is T off this also............. i don't think that hurts, but i always like to run MAP, and FPR on thier own lines with nothing else.. maybe thats just me though..

i'll see what other graph/info i can get off him regarding dwell, afr's etc..

all this info is great, slowley ruling out things

he says that no matter what they do, increase fuel, boost or timing... it surges..

at one point it was making 185hp @ 8000rpm on 11psi, 165hp @ 12psi, 150hp ??psi, and then at one stage they got it to about 200hp.. and at one point they got it to 21psi... but are plauged but the same surging..

[mattysshop]

ECU is adaptronic e420c