5 GT Turbo My C1J Forged build

[Fordy]

Turning out the mixture screw so I had idle afr around 13.9-14 helped on the return journey,

The first journey I had terrible Missfire in 5th n 4th at full throttle, soon went away tho

Still running in atm had a few blasts, up to 20ish psi, don't want to push my luck again just yet [emoji23]
Only 90 miles in so far

 

[Mark Davis]

Those miles will fly by. How many do you need to do ?

Also what sequence to you suggest when I swap head over ? Torque head down, heat car up, cool car and then re torque head bolts or a short drive and then re torque ?

 

[Fordy]

I haven't retorqued my head yet, will do it around 500 mile mark when I redo tappets. Considering I've had the head on and off numerous times the Athena gasket hasn't showed signs of leaking which I'm quite impressed with

I used arp lube on the head bolts threads and under the head of bolt, think I torqued down to 70nm or maybe 65 either way something around there works well

 

[DaveL485]

Torque head down, heat car up, cool car and then re torque head bolts

I've always done this, 20 minute run up to fan cut-in temp with a bit of fast idle.

It's the heat it needs, doesnt matter if it drives or not. The heat expansion of the metal components effectively tightens down on the gasket even more, then when it cools there will be less torque on the head bolts than spec. If you can measure the torque required to undo the bolt then do so and you will see that the bolt you did up to 70lb/ft 4 hours ago undoes with about 55, or 60lb/ft.

 

[Fordy]

Thought I'd just post up, whilst I'm suffering carb freeze at times

Spool up is pretty quick now, I'm certain I'm reaching full boost sooner, before all this work megasquirt logs showed 25psi @4500rpm dead on

Pretty sure I see 20psi by 4000 the other day but let off quite quickly

And having megasquirt controlling the fuel pump makes hot starts so much easier as it primes on ignition on now refilling the carb bowl

 

[Brigsy]

Not bad going. Mine still takes 5500rpm for 1.5bar at the manifold. I wonder if the trim etc is different on the rb unit or its just down to a fair bit of retard dialled in on my cam..

 

[Fordy]

I measure at inlet manifold base too

Got a screenshot of the log somewhere, mines just your normal 200sx s14a turbo with 64 ar housing

Want to find a pulsar turbo so I can hack together a gtx2867r by using a compressor housing n comp wheel from kinguawa turbos

 

[Brigsy]

I can remember when you posted the log up befre, its good going on a c1j. What was it like before the megasquirt? I guess a good ign map woke it up a fair bit

 

[Fordy]

Took it out to bed in the new front brembo discs and ds2500's

Started to give it some beans now,

20psi and the boost gauge was fluttering,

Came back and found my map sensor/boost gauge silicone hose from the carb had sucked together when hot, happened before.

Changed it this time to braided fuel line which hopefully won't suck closed.

Made a big difference, but found the cars going lean on boost 12.4

Used to be around 11.6 at 25psi
So clearly something is better.

Going to see if I can get a power run done local long to see what it's running as a base

 

[Fordy]

So found why my boost control is stupid atm the Tp sensor input is doing something stupid it'll work fine and calibrate perfect with engine off or on, but when you drive it it acts up,

it'll go 100% then drop to say 75% or 80% then hold there for a few seconds then go up to 130% or something stupid, clearly not good when you have 100% boost in the 70% columns, thought i was hitting overboost cut

Anyways bit of proof in the puddle,

Old engine spec was the typical setup most have,
Stock head + piper springs, stock manifolds, 1.9mm blue seal
285cam + vernier timed a little late 1-2 degs maybe 113
Carb
Gt2560 or gt2560r (commonly known as 200sx t28 60ar comp housing 64ar exhaust housing,
2.5inch turbo back system,
Big intercooler

The above setup got me 21.2psi at 4514rpm in my megasquirt datalog, Most will comfirm that these setups generally suck off boost and feel a bit flat then bam boost

My New engine spec is a little different i guess than before,

Comp ratio raised
Catcam springs with slightly more kg than pipers, bigger valve set i found fits, titanium retainers, all the valve magic 3 angles etc etc
Big ports and ported and matched inlet and flowed carb base throat area
Forged pistons, rods,
1.8mm athena
Raceland stainless manifold
Gt2560
Same exhaust system
Piper 270 cam + vernier

Above spec gets me 21.6psi @ 4442rpm, not much gain BUT the car feels so much nicer in the low down rpms, the car actually feels like its trying to move and has torque to it and more fun to drive, I can only put it down to the combination of cam and head.

Also I've confirmed at 20psi with no carb changes at any point between engine changes, the fuelling is now 11.6-11.8afr which is what i had at 25psi, now that's the part which is amazing me but also means ive got to make carb jets again and consider more carb mods maybe a bigger venturi

 

[Fordy]

Santa pod yesterday wasn't the best

First run datalogged
15.58 92mph terminal at 16psi, rev limiter was hit at 6500rpm in every gear, it bogged from 3rd into 4th and wheel spin city on the 888's

Second run the datalog didn't capture for some reason,
was meant to be 19psi as I raised the boost duty slightly

15.51 98mph, launched too softly and it didn't pick up well in 1st, 3rd into 4th didn't bog down and the car felt like it did on the road

60fts are 2.5 1st run and 2.7 2nd run

Think I might just make a efi manifold now

The carb on overrun is fueling 12afrs god knows why, then initial throttle back on goes lean 16-15

 

[andybond]

make

ORLY ?

 

[Brigsy]

To run good times with the .64 you will need a good 2 step limiter or als to build some boost. I could only go 2.1sec 60ft with the drag radials on and holding the engine on the limiter and sidestepping the clutch, compared to same launch on .49 which done 1.7sec 60ft. The .64 just felt gutless on launch as i could only make 10lbs boost in 1st gear with the drag radials on.

Rob Carnson had the same issue with the same turbo and standalone ign. He used gas to spool it which worked very well. That was my next step as a 25hp shot would spool it up no problem.

 

[Fordy]

I've got and issue with my carb atm

If I spool the turbo in 5th it does the usual 11.5 then 12.1 then down to 11.8.

But if you come off the throttle the afr's hold 12.5 and sometimes drop lower.

I'm sure that issue is magnifying mine 3 into 4th bogging

The malpassi should only be at 4.5 maybe 5 psi [emoji848]

But then I did find a 0.9 1st stage in the carb, God knows why [emoji849]

 

[Brigsy]

That could be the carb top gasket weeping into the venturi due to pressure increase. They dont last long with raised pressure. Mine has always dipped into the 9s and misfires if you spool the turbo to say 18lbs then lift to part throttle, just floods it forma split second. Only done that after fitting the malpassi, not ideal but still runs better than the 2mm needle jet. The best solution is to bin it and go efi

 

[Fordy]

Now I'm wondering,

The malpassi reg, maybe it doesn't have a huge Spring inside to return the reg to base pressure

Maybe it needs be feed a vac/boost source from the inlet manifold, as when the throttle shuts there's still boost pressure in the carb top which will cause the fpr to hold fuel pressure up [emoji848]

that new way of plumbing it means when shutting throttle off the vac pulls the fuel pressure down hopefully stopping the bogging, richness issues [emoji848] I've got a spare port on the manifold so I'm going to move it and see what the datalogs show

 

[Brigsy]

I know @Mark Davis tried the reference pipe under the throttle so it had vacuum and had issues with it leaning off rapidly at higher rpm.

 

[Mark Davis]

We tried all sorts to resolve my carb issues. 3 x different carbs, different gasket sets, different needle valve, different malpassi pressures, various jets and back to OE FPR but haven't got the experience that you guys have with carb so not sure I stood a chance.

Just go EFI Adam, I know it ain't cheap but honestly it's worth it especially if you're keeping car long term.

 

[DaveL485]

I can only put it down to the combination of cam and head.

Flow and the compression change will drive that, particularly the higher compression.

Go EFI, then you can mess with startline boost build and stuff...I can get wastegate boost with just the throttle that way. No brakes or clutch involved.

 

[Fordy]

I can build boost using launch control but it's so harsh I've turned it off till I can afford an expensive failure

Ive turned down the fpr from 5 psi to 4psi
1st stage made smaller and just cleaned the rest, so far no leaks down Venturi

Confirmed spark plugs are too hot after a 5th gear pull, so going to pull out the br8es's for br9es's

Dyno is booked for Wednesday night so I'll get some sort of figures

Dyno will either show me down on power suspect megasquirt ecu being a knob
Or that I have power and purely cannot drive it lol