924Board.org

[kondzi]

So I'm just thinking, reading through the forum again and again (as I forget after some time what I already read...) and trying to sort out few things.

S1 & S2 had different pistons.
S1 pistons with bigger dishes resulted in lower CR (that to my turbo ignorance allows more boost, right?)

S1 CR 7.5:1
S2 CR 8.0:1 or 8.5:1

I'm not sure about the stock boost, this might be completely out of specs, call it guesstimate (please correct)

931 US: 0.45bar (all years, really?)
931 S1: 0.7bar
931 S2 Euro: 0.65bar (really?)
931 S2 w/ CGT IC: 0.75bar
CGT: 0.8bar
CGTS: 1.4bar

[MikeDanger]

you really need to add an IC. honestly can't believe it didnt come with one.
and Front mount, not the idiotic top mount.

Im running 13psi. so far so good (with US 8.0:1) pulls quite good, except it goes way to rich at full boost, I can't even get any where near redline because it's too rich and starts to bog. Would be nice to see what happens if i could wind it out, but i'd already been in Jail speed at that point.
_________________
It was either this or a giant box of legos

[Cedric]

Stock internals can handle lots of power, as long as it doenst detonate, if that happens it can blow a piston regardless if you are at std power levels or at 300hp. So thats the absolute key here, sine we deal with regular cast pistons. The GT and GTS had forged pistons, probably for durability reasons since they were being used for racing.

I would not recommend going above 0,7 on an s2 ROW engine, that levels work for track aswell, but when i had waste gate line issues i noticed the knock limit is not that far away. For a pure road car maybe 0,75ish could be fine, but its not a good way to go.

I have used a knock warning over the years, its great, reacts on small changes before the ears hears it, and before damage is done. But EFI or not doesnt matter, theres not much more to get out of a std engine if you already have the correct AFR. I changed the compressor on my s2 to the larger 2664 back when i didnt have the IC, it certainly made more top end power, and less at the bottom, and ran at 0,7 instead of 0,65 bar. It had 168Hp when i dynoed it at the hubs on a very serious dyno, so it surely ran very well.

But i really really recommend an intercooler if any horesepower is being chased. You can get much more power and at a much lower risk. But if you use a std s2 compressor its tiny, and suffers alot if you boost it to 1bar, that little one is also on the CGT is probably best suited where they ran it at 0,85 bar. But hey, K26 is a big family, and thankfully theres many other compressors out there that you can fit your power targets. I used the largest turbine housing from the 931 (the 6sq cm one) and the 944TurboS compressor in combination with an intercooler. And already at standard 0,7 bar boost levels it feels and is way faster, much more low end aswell according to the datalogs, and then it pulles nicely all to the red line.


Regarding tech, no fiddling at all should be made without an AFR meter thats for sure, i wouldnt even have a standard 931 without at least testing it once and checking it. In my experience it doesnt take much leaning out on a std ROW engine before i got wild warnings on the knock sensor (had some WUR issues back when i first got my car running years ago). At 12 AFR theres risk of detonation but at 11 as it should run from the factory it can run at WOT as much as you want.

Keep to the std redline at 6500 and everything will be fine
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Cedric]

[Carrera RSR]

[kondzi]

Good stuff guys.
So keeping the stock internals first step is:
- knock sensing
- Wideband AFR

Without that there is not much sense in pushing the engine further, as without IC knock would easily appear and the cast pistons will melt (dramatizing a bit).

I’ve seen at least few times that the 931 WUR is giving overly rich AFR under boost, encountered that also myself. However, there is a screw from the bottom of the WUR (behind the plug) that should “lock” the enrichments. I screwed that in when tinkering with my WUR recently, but haven’t had chance to verify the effect.

I don’t believe this is what is supposed to be with overly rich under boost. I’d like to keep CIS in my car, knock/ign retard I can manage via my standalone ECU.

Next step would be installing intercooler.

And another one - upgrading the turbo.

This path seems reasonable to me. 300HP+ for me is to much in 924.
But going over 200HP by just adding IC and good monitoring seems a really good idea.

So what is the limit for the S1 and S2 turbocharger? 240HP?

For a street car the bottom end would be more important, so a smaller turbo seems to be a better choice - therefore the “new” turbo with better efficiency would be preferred (not everyone is chasing HP).

Torque-wise, this also could make sense. What about those turbos with the possibility to change the angle of the rotors (sorry for my lack of knowledge of English words to describe it in proper technical language). This seems to be driven by a step motor, that could be controlled by the Standalone ECU.

I’d prefer the smaller turbo that spins faster, rather than a big turbo lag and lots of unusable HP on the street.

Then the exhaust manifold - stock is quite short and to my understanding allows the turbo to spin up faster as well. So keeping it (also for a cost reason) and adding just a short 3 bolt to 4 bolt adapter to fit the new gen small turbo could be optimal when not building a monster?

The intake part - adding FMIC equals lots of piping. The more pipes and the bigger the diameter, the bigger turbo lag. So let’s say targeting the 220-240HP with either stock turbo or a small new gen turbo, what diameter of pipes would you advice?

Smaller HP target also means a smaller IC is needed. That should be easier to fit. Maybe a smaller but more efficient radiator then and a small IC would fit side by side - what do you think?
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)

[Cedric]

The thing with the WUR and the enrichment is that its works perfectly when the car is standard, but as soon as you make any changes it will also change the fueling, how it does that depends alot of many parameters such as the turo size. My was perfect in std form, the AFR was flat at 11 all the way to redline. But when i put the turbo and intercooler on it changed alot, and it went way richer. You can changed the boost enrichment on the screw, but I also tried putting a pressure regulator on the control line to the WUR. In the end i just pulled the boost line completely from the wur and the AFR ended up good. You just have to try and see what your car wants.

Updating or putting on a different compressor side(like audi 100, 944turbo etc) on the standard turbo makes intercooler updates much easier, since you can rotate the compressor freely and it makes boost pipes easier. Check my thread for some inspiration

See what turbo you have and we can see what it is. If you have a standard s2 ROW turbo it can work for a bit over 200hp with good reliabilty, but as i wrote before the standard compressor is hard to work with when it comes to IC. A mitsubishi TD04 turbo would be very nice and super responsive

The log manifold is good for boost response at low engine speeds, so it should work fine for this. The boost piping on the compressor pipe dont affect response much at all, ive done some tests with this that very it, do as you want to make it fit

Just remember that if you have a very small turbo you might need an intercooler that can handle both the temperature and not create alot of pressure drop, since pressure drop will eat out of your compressor capacity. Its not so hard to put a fmic infront of the radiatior, just some small cutting or spacing out of the radiator.

Honestly for the twisty country roads that we have here i think i probably enjoy my car more in the 200hp region, at 1bar when it whould be around 245hp i think its a bit quick to reach very illegal speeds. So i agree to aim at the 200-220 hp with good driveability.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Cedric]

This was my piping system when i took the engine out, the pipe of the left will be changed to a 2inch pipe to get more clearence, its extremely tight there.



Regarding the different compressors on the K26, heres my rough hp numbers based on my simulations and experiences, and not to rev the turbo to the moon, which will shorten the lifespan of the turbo. You can always overrev them and get more flow, though its not recommended. The power numbers below seems to also correlate well roughly to the size of the compressor, (inlet area which roughly dictates flow)

2470 (row s1) 200hp, its shite ancient design with low efficiency, even if its not the smallest by flow area.
2660 (more modern design but tiny, maybe 210 like the CGT leaves it in a good spot.
2664 (same design as 2660, on Us cars, and put on some ROW cars as replacement turbos) 240hp
2667 (951) 260ish
2670 (951 TurboS) 280ish
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Carrera RSR]

First job is a good and efficient FMIC, without which all other mods are futile

K26 2664 6.10 or 4.10 turbo
Adjustable WUR
Possible fuel enrichment delay. I did this to avoid going rich too early
Modified fuel dizzy to push 15-30% more fuel. Will be needed for +220bhp and 1.0bar boost at the top end
AFR + Knock sensors + dyno time
Making stock waste gate dual port with pneumatic air regulator to manage counter boost on top port. The top port has a 'mushroom' vent on it. Remove and attach banjo fitting and pipe back to air regulator.
If pushing onwards from 220-240bhp then thats when forged pistons, ARP head studs and Cometic HG starts to make sense.

Along with Cedric's posts, also check out mine car thread. Whilst everyone wants more power, which is fine for dragging or pure race, I'm finding even with LSD and R tyres, that some respect is needed when pushing on the road, track or hill climbs. Or I'm getting too old.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

[Cedric]

With an S2 fuel system there seems to be no modding needed for 240ish hp with the right sized turbo. But somewhere there I seem to run out of fuel at the top end around AFR 12. The only way to find out how far the system works for the setup you have is to try step by step and see what it needs. I also noticed that not all wurs are fully the same either when measuring AFRs at full power.

HG issues might arise, like for me, the cars are old by now, as is the head gaskets. And the blocks arent flat anymore, since they are old.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[MikeDanger]

couple things. The Allen on the bottom of the WUR, DOES NOT stop the boost enrichment. its spring loaded, if you screw that in you will screw up the A/F across the board.

I also disconnected the vac line to the WUR, didn't help.

Infact the best way would be to have MORE vac to the WUR to pull back fuel(or some how flip the position of the port so that the boost pushed the diaphragm the other direction )


I ALSO, cut the wire on the TB for WOT enrichment..... Still have too much fuel at WOT at full boost (13psi)
_________________
It was either this or a giant box of legos

[kondzi]

First things first guys.

It seems the 220-240HP (at crank) range should be somewhat easily achievable with not many mods needed.

For me the ECU/sensors/ignition part is easy.

The remaining part needs some rethinking, as I'd like to have that in small factor, compact

1. Standalone ECU to drive ignition/retard when reaching knock [already there, but maybe will change from MegaSquirt 2 to something more modern]

2. AFR (just for monitoring, as staying with CIS) [already there - Innovate LC2]

3. FMIC Intercooler for 220-240HP
- what size,
- what shape,
- Chinese tuning stuff or OEM/951

4. Turbo (integrated Blow off preferred)
- new or refurbished or new aftermarket?
- 951 or 951S might be availability/price issue (read somewhere on forum that only cold side is needed - new or used?)
- newer turbos are water cooled right? - need for additional piping and electric pump
- new generation turbo (i.e. Mitsubishi TD04 family seems to be early '80s to like 2010+, which exactly you have in mind? is it really new generation turbo?)
https://wikicars.org/en/Turbocharger_application_guide
- my choice would be to aim for a turbo from something recently new and produced for mass market (like VW Golf or Mitsubishi Lancer or so)

5. EBC/MBC with banjo on top of Wastegate and return pipe

6. WUR / Fuel Delivery - to be sorted out after points 1-5 done (going to rich is considered safe)

PS. I have considerably new HG (Victor Reinz) and both the head and block were made flat before assembly.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)

[Cedric]

[kondzi]

The turbo I have was rebuilt by PO.
The thing is I don’t know what it is, as when I was reassembling the engine I didn’t care at that time about what it is exactly

Integrated blow-off and WG, that might be interesting to fit.

For the IC.
I have changed the stock radiator fan to SPAL so I have some more room there. Need to check, maybe spacing the radiator to the back would allow to fit there IC and piping without much effort.
I can weld aluminum so modifying a fully aluminium IC might be a low budget option as well.

For the ECU - I have an Ecumaster Black laying around that I bought for my 911 project, which is now in the freezer, so I was thinking to utilize that one. It has a really nice knock-sensing feature, integrated WB controller and much more cool stuff. And it’s made in 21century SMD and CNC machined case with sealed automotive connectors rather than DB9 and DB25 from the 70’s

Time to do the homework.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)

[Cedric]

If you can weld aluminium you can also weld up some nice new brackets, shouldnt be to complicated. I also have a spal, otherwise IC piping would be a mess to do.

The ECU master black is a nice unit, would be a very nice thing to have for sure. You could also plug in some additional pressure and temperature sensors if you would like to log what the engine is doing, or have some warnings, or engine protection strategies.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/