Sputtering under load and idle

[joseph0205]

Sputtering under load and idle

Ok so i refitted the turbo to my 97 R33 GTS-t on the Christmas break and have noticed that under load (say 80km/h in 5th or 60 in 4th) if i put my foot down the car will reach about 2.5K and start jerking and sputtering eventually evening out at 3-3.5k. when i first noticed it i was running 91 from united (so it was probably half water anyway) so i ran a full tank of BP 91 and injector cleaner through it and the problem was less noticeable but not gone completely. the next step was to run bp 98 through it to see it i was just running too low of an octane rating which didn/t change anything (what is the downside of running a lower octane BTW, engine damage or just terrible economy/running?). also sometimes when cold (idling at 1.5k to warm up), the engine will slightly miss every couple seconds but i assume this might just be a sign of the cars age. So am i looking at rubbish injectors or should i start looking at the coils or spark plugs (the plugs probably only have 10k on them and no idea about the injectors or coils).

For note the car is running just off stock (basically pod filter, front mount, a 3.5" exhaust and bypassing the 2-stage boost controller)

Cheers guys   

Edited April 1, 2017 by joseph0205

[GTSBoy]

Just about anything could be wrong with the car.  Serious.

But first and most important, if you ran 91 RON fuel in it, and made boost, it WILL have been pinging.  you could have caused serious damage to the pistons, head, spark plugs.  It could be fatal.

[niZmO_Man]

Turbo = 98 RON.
Your car would have been knocking quite hard, drain the fuel tank and fill with 98. Check the spark plugs, change to BCPR6ES (no -11 at the end).

Pod filter might have lead to dirty AFM, so clean it with contact cleaner.

[tridentt150v]

Check your coils for cracks, wrap in insulation tape to fix...could be arcing.

98 98 98 98....never use anything less.

gap plugs to 0.8 [ I think it is, my memory is killing me].  Even if you have 11's just tap them down, no big deal.

We are all assuming a std turbo and ECU???  What boost?

 

 

[joseph0205]

2 hours ago, tridentt150v said:

98 98 98 98....never use anything less.

yeahh the price between 91 and 98 was close to 70c/l different (it was a very remote servo) and i didn't think it was as bad as you guys have mentioned, it was also all open highway driving so i wasn't really pushing the car hard at all.

2 hours ago, tridentt150v said:

We are all assuming a std turbo and ECU???  What boost?

 yeahh stock turbo and ECU running wastegate pressure (9PSI i believe) all i've really done to the car since owning it is get it back to stock plus the FMIC, intake and exhaust system and bypassing the 2-stage boost control, it also has a aftermarket BOV but i believe the previous owner just added it for the extra wank factor. 

 

also i recently cleaned the AFM while reinstalling the turbo but i might hit it again

[tridentt150v]

Ditch the aftermarket BOV...too many problems.  Some of which sound like yours!!!

[GTSBoy]

8 minutes ago, joseph0205 said:

 bypassing the 2-stage boost control, it also has a aftermarket BOV but i believe the previous owner just added it for the extra wank factor. 
 

Congratulations.  In theory, you should have 5 psi of boost.  You'd be better off leaving the factory boost solenoid in play!

There's a strong chance that having only 5psi should help stave off the worst detonation.  Although 91 octane is goats' piss, so no bets will be laid by me.

I echo the call to block the BOV and test again.  Venting BOVs are the single most stupid thing to put on an AFM equipped standard ECU anything car.

[joseph0205]

9 minutes ago, GTSBoy said:

Congratulations.  In theory, you should have 5 psi of boost. 

from everything i have read it allows the turbo to push the full 7-8 psi at all times/well the engine can actually physically make that much boost using the grounding trick from this forum. also the BOV is GFB branded and can fully recirc which is what i always run it on anyway, can it still be causing the problem?  

[GTSBoy]

Wrong.  The R33 wastegate actuator is a 5psi actuator.  The ECU's boost control solenoid is switched to open a controlled bleed of the boost from the turbo, which raises the boost to 7 psi.  If you directly hook the boost signal to the actuator, you get no bleed, therefore you get no boost increase. You get 5 psi.

And does the BOV fully recirc, or is it can?  Is it plumbed up recirc with no external venting at all?  If it has any venting at all, it could be causing troubles.

Edited April 6, 2017 by GTSBoy

[joseph0205]

2 minutes ago, GTSBoy said:

The ECU's boost control solenoid is switched to open a controlled bleed of the boost from the turbo, which raises the boost to 7 psi.  If you directly hook the boost signal to the actuator, you get no bleed, therefore you get no boost increase. You get 5 psi.

ok so maybe it was my choice of the word 'bypassing' that was wrong, the boost controller and all of the vac lines run exactly where they would in a stock car, all i have done is grounded the signal to the solenoid (from the ECU ) so it it thinks that the car is doing 4500rpm or what ever is needs to trip the "high" boost mode in the ECU (the original post that im referencing is here: 

 

7 minutes ago, GTSBoy said:

And does the BOV fully recirc, or is it can?  Is it plumbed up recirc with no external venting at all?  If it has any venting at all, it could be causing troubles.

The BOV is plumbed straight back into the front of the turbo and IS fully recirculating unless they are designed to have a small opening even when in fully recirc mode (but i assume this wouldn't be the case) i also cannot find/hear any leaks on this recirc line. 

[GTSBoy]

OK, so first up, at least the "bypassing" is giving you high boost.  That means 7 psi, not 9, unless a bigger exhaust is helping to reduce restriction.

There's no RPM involvement in what you're doing either.  You're not tricking the ECU into anything.  You're just forcing the solenoid to be on by earthing the solenoid, which is what the ECU does when it switches it on.

And the BOV should be fine.

But all of this is not good news, because it would have been better to be running lower boost, and it would be better if the BOV was to blame.

[joseph0205]

i wasn't too sure on the 9psi number thats why i wrote "i believe" basically i know it runs around the 350mmHg mark on the stock boost gauge and i did a very rough conversion and came up with 9ish. yes i know that im not trick the ECU i also explained myself poorly again obviously, i was just simply trying to say that there is no need for the car to be at 4500RPM to trigger the ECU to allow the boost gauge up to the fully 7psi yet also allowing the ECU to not freak out that the boost controller isn't working.

the rest of it thought doesn't sound so positive, i will try gapping the plugs down to 0.8mm before i go throwing massive money at new coils when i have some spare time (bloody mid-sem exams ) 

[GTSBoy]

Just for clarity....the ECU doesn't care whether the solenoid is hooked up or not, plumbed up or not, wired up or not.  Just doesn't care.  As far as I know, there's no 4500rpm threshold in the ECU logic either.