Fj20 Multiple Dyno Problems, Wastegate Issues To Down On Power

[Gareth87]

Hi everyone,

Ive got a strange set of problems that i would like some opinions on so i will explain in as much detail as possible.

My FJ20 was tuned over 2 years ago after it was built and it made 395HP at 17psi. A few weeks ago i took it back to the dyno to give it another power pull just to be sure everything was sweet. As i rocked up to the dyno, i put a new set of plugs in it just because it hadn't had plugs for 2 years. Anyway it made 394HP so everything was fine and i was satisfied.

I took it to the drags 2 weeks ago and on the first pass it felt like what was a fuel surge just before the line so i shut off and rolled over.

I was concerned that i had hurt the engine so i did 1 more pass short shifting a little earlier and still did the same MPH, this time without the fuel surge so i figured everything was ok.

Paranoid, i took it back to the dyno to do another pull to make sure everything was all alright. The first run it only made 375HP followed by 370HP on the second pull. Boost was also coming on later by about 500rpm but holding 17psi when it came on. We figured something was wrong so did a comp test straight away on the dyno which came out with all cylinders between 185-190.

Satisfied with that, Next we put a pressure tester on the front of the turbo and pressurised the system, the only thing that we could hear leaking was what was sounding like the inside of the external gate. Strange..

While the plugs were out, we inspected them which showed that 1,2,3 were fairly even, but 4 was very rich. (possible plenum design, see photo below)

Anyway, so we cleaned them and got straight into the power pull.

The first run, boost came on super late, by over 1000rpm and then went on to pull 395HP again, followed by a backup run at 391HP.

I pulled the plugs again and number 4 was definately rich still, but the power was back.

I have no idea why this has all happened and i know its a hell of a story, but if anyone has any ideas i would like to know. The only additional thing i can think of is that it was stalled backing onto the dyno and flooded, and took a while to get it started. Perhaps fouling a plug? but i dont know.

So to recap.

Boost on late - hissing noise in external gate. (turbosmart pro gate 48mm)

Power down but picked up with clean plugs.

1 rich plug - wondering if plenum design isn't very good.

Flooded before initial runs, could the plug have fouled causing lack of power?

Best pics i have of plenum

Thanks for the input,

G

[R31Nismoid]

Having seen many many custom plenums - most of them (well, all) taper. Start large, end up smaller.

Yours is just like a long tube.

There will be a reason for it to taper im sure, big companies don't spend big bucks for nothing... what that is though, no idea!

[Guilt-Toy]

yes that plenum design is rubbish. its obvious cyl 4 is not getting as much air flow as the rest of the cyl.

what ecu are you running? you are describing microtech to me =)

btw, how do you keep the ass end together with all that power in a blue bird?

[Gareth87]

The plenum design i felt worked a lot better when i was making a lot less power, i used to get fairly even plugs then, however, I'm 22 now and built that plenum myself when i was 16, I was learning just how a turbo system works then, so i couldnt even have guessed it would be making 400HP a few years later.

The rear end is a 10 bolt series 3 TRX disc rear with a detroit locker centre and 4:11s. The trailing arms are welded and plated so touch wood, its not too bad so far.

I run a Wolf ECU V4. So definately not the best thing in the world.

Will running that cylinder so rich become a problem? i have been told a resistance check of the leads may show something up as well.

G

yes that plenum design is rubbish. its obvious cyl 4 is not getting as much air flow as the rest of the cyl.

what ecu are you running? you are describing microtech to me =)

btw, how do you keep the ass end together with all that power in a blue bird?

[STATUS]

can you get an IR temp gun and check the exhaust runner temps on the dyno (crude but i doubt you have egt in each runner) i would compare 1234 especially 2 and 4 and see what the diff is, you will have to do it mid pull.... not nice or safe leaning in a red hot bay,

[Adriano]

I would have a look at the dizzy capa nd leads , maybe #4 is missing. I would have thought #4 cylinder would run lean with that plenum, with the pressure banking up at the back.

Edited December 20, 2009 by Adriano

[Guilt-Toy]

nice, that is one damn cool car! i would like to see some pics of it if you don't mind

anthonye at skylinecentral.org

The plenum design i felt worked a lot better when i was making a lot less power, i used to get fairly even plugs then, however, I'm 22 now and built that plenum myself when i was 16, I was learning just how a turbo system works then, so i couldnt even have guessed it would be making 400HP a few years later.

The rear end is a 10 bolt series 3 TRX disc rear with a detroit locker centre and 4:11s. The trailing arms are welded and plated so touch wood, its not too bad so far.

I run a Wolf ECU V4. So definately not the best thing in the world.

Will running that cylinder so rich become a problem? i have been told a resistance check of the leads may show something up as well.

G

[Gareth87]

hey guys,

Thats not a bad idea with measureing the heat of the runners, have to go back to the dyno though. I might get the injectors checked as if #4 is a bit dodgy, then it may be leaking at idle or something. I thought the plenum would favour cyl 4 however, its curved around feeding the air in there. Also, with a turb like a 3040, it should have enough CFM of air flowing through that plenum to keep up with the cylinder. But im very open to the opinions here because it was only my guess.

I also built myself a pressure tester today to pressurise the inlet system and i've definately got a leak in the gate somewhere. Air is pissing out from between where the valve shaft goes up into the head of the gate. That was only with about 12psi showing on the boost gauge. I'm guessing thats not normal hey?? would that cause a slow spool up?

Im still stumped why it would run 25HP down for 3 runs until i cleaned the plugs and the HP came back...

(thanks guilt-toy, ill flick some pics over!)

G

Edited December 21, 2009 by Gareth87

[Guilt-Toy]

I have a bit of a soft spot for blue birds because it was my first road regoed car and a soft spot for FJ's as it was my fist boosted car in a 180b sss

hey guys,

Thats not a bad idea with measureing the heat of the runners, have to go back to the dyno though. I might get the injectors checked as if #4 is a bit dodgy, then it may be leaking at idle or something. I thought the plenum would favour cyl 4 however, its curved around feeding the air in there. Also, with a turb like a 3040, it should have enough CFM of air flowing through that plenum to keep up with the cylinder. But im very open to the opinions here because it was only my guess.

I also built myself a pressure tester today to pressurise the inlet system and i've definately got a leak in the gate somewhere. Air is pissing out from between where the valve shaft goes up into the head of the gate. That was only with about 12psi showing on the boost gauge. I'm guessing thats not normal hey?? would that cause a slow spool up?

Im still stumped why it would run 25HP down for 3 runs until i cleaned the plugs and the HP came back...

(thanks guilt-toy, ill flick some pics over!)

G

[STATUS]

I have a bit of a soft spot for blue birds because it was my first road regoed car and a soft spot for FJ's as it was my fist boosted car in a 180b sss

haha mine too... sies III wagon cause i was a surfy dude.

[discopotato03]

Yeah my first RWD/then EFI/then turbocharged car .

I bashed out a long post this morning but lost it to cyber space .

1) Early non intercooled DR30 Skylines had the largest plenum volume OE FJ20 inlet manifold .

2) I used an S12 Gazelle clutch master and a brake master/booster from a JDM Bluebird SSS .

The trick is to separate the rear from the front half of the boosters chamber and turn it 180 deg to offset the whole assembly downwards . Then you can fit a DR30 manifold on an FJ20 in a Bluebird , must also use the OE manifold brace or the mount nuts come lose .

If you must use an Oz spec booster/master pull the booster out and unbolt the aluminium mount off the boosters two rear studs . Rotate it 180 and bolt it back on . Makes them sit lower .

Really better off geting an early MR30 Skyline booster and having it rebuilt with longer rear studs , std too short for a Bluebird but same pattern .

JDM Nabco or Tokiko masters are MUCH better quality and larger bore ie 15/16 than the Oz birds 13/16 Girlock piece of crap .

3) DR30 Skyline front struts bolt into Bluebirds but one of the line fittings is non std onthe hardline side of our Blueys , change it and all falls in .

4) Rear four link and H190 ok for straightline use , resist temptation to use urethan bushes in the rear because the top diagonal links work in different planes to the lower parallel ones .

5) Takes lots of work to get a decent radiator and intercooler into a Bluebird , I used an R32 GTR rad and a pair of DR30 elec fans . Cooler was an early Plasmaman and the bonnet latch was converted to a 1600 Datsun type . Headlight inner mounts were loped off and new ones made .

GTR rad pins sat on sockets welded onto the removable caster rod brackets in rubber bushes . Also lower mounts for the fan shroud went into those brackets . I had a steel pipe made up to transfer water across the bottom because GTR rad and FJ20's are opposites so to speak .

6) Gearboxes , the best of the 71 series boxes was the manual R32 RB20DET ones . You take the FJ type bellhousing and bore its lower bearing tunnel accurately out to suit the RB's larger lower bearing and then fit the RB's front bearing cover/clutch bearing spigot . RB 71 boxes have the wide gears and all big syncros . I know people slot the top bell housing bolt holes on RB bellhousings and flick one of the dowels but that's the bodgey way to do it .

Almost 10 yrs and lots of resources went into my Bluey , it was engineered and legally registered in NSW with TRX910 plates .

I couldn't get 7 for it in the end even with a DR30 IRS R200 LSD rear end/Autronic/Bilsteins etc .

Parted it out and made almost 7 so far in bits . Last I saw the shell was on the back of a truck with the cranes boom through its roof . Such is life .

A .

[Guilt-Toy]

hahaha!! Mine was series III sedan! Good ole ca20.. man i won some bets about the 8 spark plug thing.. i ended up rebuilding it.. thing had 210psi compression per cyl ! could only use very expensive head gaskets the cheap ones would die straight away

haha mine too... sies III wagon cause i was a surfy dude.

[Gareth87]

A little update, i pressure tested the system again yesterday while i had some time and it wasnt costing shit loads sitting on a dyno.

The external gate is leaking big time out between the shaft and where it goes up into the head of the gate. I rang turbo smart and they said its a worn valve guide leaking boost. I can only assume this is causing my problem of boost coming on slow. They said the 48mm progate which is what i run is outdated and may be hard to repair. Man i was pissed off, its got less than 10ks on it and its not even a track car! bullshit.

Anyway, assuming that when i repair the gate, the boost should come on earlier again, its now down to why did it do 2 runs low on power and why #4 plug is fouling?

Still need to try the above options when i get time. The gate cant be fixed until mid Jan, when they get back from holiday anyway.

G

[Gareth87]

Hey guys, i just had my injectors cleaned about half hour ago and they were pretty much fine. In fact, #2 was pumping out the most fuel. But they were all within a 4% tolerance.

I need to check the lead to that pot now but i think the fuel side is fine.

Would that cylinder running rich cause any problems? if there was enough fuel for it to glaze i would have thought it would show by being down on power or drive poorly or something. Does anyone think it will be a problem to drive?

Also, i had the radiator rebuilt and cleaned which i picked up today. He said it was around 20% blocked. Which isnt much, but maybe enough to creep up the temps at idle.

Anyway, opinions on the injector situation would be great. Or do you still think its the plenum design even though ive had good plugs colours in the past.

G

[Adriano]

Have you measures the lead resistance, i would say #4 fouling is more likely related to an ignition problem than overfuelling.

[Gareth87]

I just measured the leads then, i think i was using the multimeter correctly, (had it on the 2000k setting)?

Anyway,

#1 - 10

#2 - 13

#3 - 16

#4 - 12

I have no idea what im looking for with leads so any info would be great. As it runs an electronic dizzy, is it worth checking anything there?

Thanks, G

[T04GTR]

interesting.

have you noticed any extra timing chain rattle on start up?

not meaning to scare you but when mine started playing up it dropped the lower jackshaft chain and f**ked the motor...

might pay to pull the roker cover off and check if the cam timing is ok and the ignition timing is as it should.

have you got a cat converter? check its not melted.

it would have to be a very big leak to reduce power. but.. it has nothin gto do with lag. if anything the oposite, as once the exhaust is leaking past the guide, the gate must be open, ie: on boost, so if anything it will overboost as the boost presure will be leaking past the guide intoducing a airleak in your wastegate plumbing.

thats a gt35? have you checked the turbo shaft play? also are they rx7 injectors? i put them in my fj20. the fuel line i squeezed over the end of them had the inner shieth bunched up on the end of one of the injectors resticting it. and i melted a piston.

with your plenum, not great. you should use the factor turbo one. dr30. use a 180b brake booster. much smaller if thats why you changed it.

also the na plenum is bigger and has slightly smaller runners and will give you better midrange without any loss up top. use a xf falcon throttle body.

[Gareth87]

Hi To4GTR,

Thanks for your reply, i can answer your questions to me no worries,

There is no extra timing chain rattle, in fact, i get no timing chain rattle at all.

No Cat in it, as engine is pre 85.

The gate was leaking boost pressure, ie, when i pressurised the system by putting a blanked off silicone tube over the comp cover with an air fitting on it and pressurising to 20psi, it was pissing air out of the gate. This is now resolved.

Turbo is fine, has less than 10ks on the turbo and 0 shaft play. The RX7 injectors which are in it, were tested last week. All fine as well.

The next thing is the manifold, i think a standard manifold is most probably better also, but i have had even plugs before with the same manifold. I think however, a custom plenum is next on the agenda.

Would a different heat range plug help?

G

[FJdat]

what brand/heat range plugs do you run and how old are they?

Edited January 17, 2010 by FJdat

[-troy-]

Hi To4GTR,

The gate was leaking boost pressure, ie, when i pressurised the system by putting a blanked off silicone tube over the comp cover with an air fitting on it and pressurising to 20psi, it was pissing air out of the gate. This is now resolved.

Turbo is fine, has less than 10ks on the turbo and 0 shaft play. The RX7 injectors which are in it, were tested last week. All fine as well.

G

Hi Gareth,

I was one of the first Turbosmart reps you spoke to about this. You probably didn't know, but that last guy you spoke to, was Nic, the owner of Turbosmart . I think he was kind enough to give you a free valve guide considering.

This issue was discussed among the tech staff and collectively, we have never come across an issue like this where it was the gate (Leaking or otherwise). The leak in your gate was marginal and technically would improve your power curve.

Can I reiterate what was discussed the other day, which is your AFR is way too rich. We suggest you find another tuner for a second opinion on the AFR values.

What stands as the first glaring issue, was the sheer density of soot in the outlet of the gate. It is running extremely rich on boost and if that gate came off after a power run, it is running too rich across the boost range. The amount of soot would indicate something in the 9.5-10.5 range. Consequently, comparing to your first power run, your plugs will foul up giving you a much weaker ramp up on the next run. This would get even worse if there were no air temp compensation values, allowing it to run richer as the air got hotter and thinned. This is something that would give you those graphs also. Your first, slightly cold, run would have been pretty good but as the car got hot, it got richer and would retard your spool up.

In contrast, you will find quite a few tuners will lean out the lower rev range in certain areas, to improve spool up.

The above is merely opinion and we strongly advise you consult a qualified and well experienced tuner before making any changes.

Hope this helps.

Cheers,

Troy