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morghen
Joined: 21 Jan 2005
Posts: 8879
Location: Romania
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 Posted: Tue May 23, 2017 6:10 pm Post subject: |
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Very nice, has all the right bits.
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Sat Jun 03, 2017 9:39 pm Post subject: |
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Went out for a drive last evening in great perfect weather, sunny and cool at about 18-20 Celsius. I cranked the boost back up to 12lbs from 10lbs, what a difference that makes. I had it up to 12 before but didn't remember how much of a difference it makes on the butt meter. 
Now I'm curious to find out what is the difference between 12lbs and 14.7lbs (1 bar)???
I might be able to safely go to 14.7lbs of boost when switch to the GTS intake with a FMIC about 2 x larger than the GT TMIC combine with the low compression ratio of the S1.
Thoughts?
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Sat Jun 03, 2017 9:49 pm Post subject: |
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Be careful above 12PSI!
Don't rule out water-meth injection. It is cheap, easy to install, and remarkably effective. The only downside is that you will want to top off your reservoir before each drive, and carry extra with you in the car.
Remind me what turbocharger combination you're running?
I'm putting a hybrid 951S K26/8 into my Holbert super wide, which can easily support 350BHP, and is supposed to have much higher adiabatic efficiency in the 1+bar boost range. My goal for that motor is a comfortable / streetable 250-300 BHP range.
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Sat Jun 03, 2017 10:17 pm Post subject: |
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| ideola wrote: | | Be careful above 12PSI! |
Could you elaborate on this? Is it because of the turbo efficiency range, engine internal components or heat charge?
I'm running stock S1 turbo, K26-2664 G 4.10
Should be fair to assumed that a FMIC will be more efficient at cooling charge than the TMIC due to location and size.
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Sat Jun 03, 2017 10:44 pm Post subject: |
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The standard K26 is just not efficient enough to operate for long periods at that boost level. Remember that as boost increases linearly, the heat increases exponentially, so it is not a 1:1 increase in temp with boost increase.
While the FMIC intercooler itself will be more efficient than the TMIC, the total FMIC system may not give you quite as much increase due to the extra 90 degree bends and length of the path. The TMIC is a beautiful piece of engineering because the path is so direct.
The point being, while you may pick up some incremental cooling with the FMIC, it will not be exponentially more efficient than the TMIC, an likely not enough to offset the exponential increase in heat from an inefficient K26 running at 15PSI.
There's a reason the 937 was limited at 12PSI. There's a reason the GTS/GTR/GTP variants all had lower compression pistons than the 937, and also had different (i.e. more efficient) compressors on their turbochargers.
I understand the desire to run the FMIC and the GTS intake. But the limitation you will be bumping up against is the K26 compressor. Old technology, and highly inefficient in the range you want to run. In an ideal world, you would address the constraint directly by improving the compressor side of the equation, rather than trying to "band aid" the known weak point with less than optimal solutions that won't keep up with the heat.
My recommendation would be to consider upgrading the turbo at the same time you change over to FMIC and GTS intake. The 951S turbo charger is direct bolt on, just replace the 951 turbine housing with your 931 turbine housing (or, ideally, a 6.10 housing if you can find one). That K26/8 will run all day at 15-17 PSI at optimum efficiency. Intercool that...colder denser air makes more power...and I think you'll be happy as a pig in shit (as they say down south).
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Sun Jun 04, 2017 12:28 am Post subject: |
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I see
Any drawback or other modification required to go with the k26/8?
At what RPM boost start to build?
At what RPM full (lets say 15lbs) boost should be expected?
Will I need to do pluming for water cool?
Others?
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Sun Jun 04, 2017 1:20 am Post subject: |
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| 924-76 wrote: | | Any drawback or other modification required to go with the k26/8? |
None that I have identified yet.
| 924-76 wrote: | | At what RPM boost start to build? |
This is mostly (though not entirely) the function of the turbine housing. So you should decide which housing you want; in my experience:
- early S1 6.10: boost starts around 3000, full boost around 3500, pulls strong past redline
- late S1 4.10: boost starts around 2500, full boost around 3200, pulls strong to 6000ish RPM
- S2 4.10: boost starts around 2000, full boost around 2800, runs out at 5800
S2 is a good setup for street drivability, but not so good for my taste on back country roads or twisties where I prefer to wind it out. I love the character of the 6.10 hotside. People complain about it being laggy, but that is something you can adjust for based on how you rev the car and where you shift.
| 924-76 wrote: | | At what RPM full (lets say 15lbs) boost should be expected? |
This is a function of how the hotside and coldside work together, and I can't tell you from experience (yet) what to expect. Unless I can find a 6.10, my K26/8 will be running the late S1 4.10 hotside, so I expect full boost between 3000-3500 RPM.
Two other mods that greatly aid in faster spool / better response:
1. ceramic coating the entire exhaust tract: manifold, turbine housing, down pipe, j-pipe, dump pipe, lower wastegate housing.
2. leave the stock US-spec 6PSI spring in the wastegate, and install a manual boost controller; plumb the outlet from the boost controller into the vent port (upper chamber) of the wastegate. This prevents any creep of the wastegate diaphragm, conserving all of the exhaust heat and energy for spooling the turbo until the exact moment that your desired boost pressure is achieved and the wastegate then opens up. I believe this mod is vastly under-valued as a way to improve the throttle and turbo response.
| 924-76 wrote: | | Will I need to do pluming for water cool? |
Water cooling circuit is not required. Many 951 guys eliminate it. So there is no reason you can't run the bearing housing simply as oil cooled, and add the water cooling circuit later if you so desire.
One other thing to consider is using a Cometic headgasket to "dial in" the compression ratio you want for the desired turbo charger configuration and boost level you plan to run. Personally, I prefer to run higher compression pistons with less boost, than to run lower CR and higher boost. The former arrangement will generally be more reliable and less stressful on the engine. The latter will allow higher top end power at the expense of more lag and sluggish response off the line. In this config, the engine will feel more "peaky" where it has no guts off the line, but then when the higher boost kicks in, "WHAM!" you're off and running. So it really depends on what kind of driving experience you're wanting to create.
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Sun Jun 04, 2017 8:06 am Post subject: |
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Thank you for all the info, something I will definitely consider for the future.
I think I would use the late S1 4.10, which I'm currently running.
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP |
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Sun Jun 04, 2017 8:10 am Post subject: |
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Today I was able to finish painting of my spare moon-roof.
Not as nice as what I did last year, but still happy with the result.
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1976 924 N/A ROW SOLD
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ideola
Joined: 01 Oct 2004
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Location: Spring Lake MI
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| Posted: Sun Jun 04, 2017 11:24 am Post subject: |
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That's awesome!
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Mon Jun 19, 2017 4:07 am Post subject: |
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| ideola wrote: | | My recommendation would be to consider upgrading the turbo at the same time you change over to FMIC and GTS intake. The 951S turbo charger is direct bolt on, just replace the 951 turbine housing with your 931 turbine housing (or, ideally, a 6.10 housing if you can find one). That K26/8 will run all day at 15-17 PSI at optimum efficiency. Intercool that...colder denser air makes more power...and I think you'll be happy as a pig in shit (as they say down south). |
What is the K26/8 part # I should be hunting for?
Thanks
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1980 931S
1981 931 Part car RIP |
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Mon Jul 24, 2017 8:18 am Post subject: |
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After studying multiple GTS engine bay pictures, I realized that the original GTS has an intake vacuum connection at the back where the 5th injector connect:
I wanted to keep the installation as simple as possible. It was suggested to use the re-circulation valve connection (under side) as vacuum connection, but that mean modifying the hard pipe as it is a pretty tight fit down there.
So I had an aluminum connector made to fit between the intake and the 5th injector to replicate the original setup.
And a modified barb connector to fit the intake.
Also, since I was uncovering my valve cover by removing the GT intercooler, I figure it was a good occasion to give it some attention.
Before
After
More to follow...
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP |
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Carrera RSR
Joined: 08 Jan 2010
Posts: 2309
Location: Somerset, UK
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| Posted: Mon Jul 24, 2017 6:02 pm Post subject: |
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A summary of my experience pushing the limits of my car with an eye on CGT and GTS spec motors etc. ......
My front bumper ducted 951 FMIC cools 1.1-3bar circa 6 deg above ambient despite pushing the 2660 6.10 beyond its efficiency. Post turbo air temps can be over 125deg. Post FMIC brings it down incredibly well. In the UK we rarely see air temps over mid 20's in the Summer. So post FMIC intake temps usually sub 30 on most days. Far less in Winter.
More boost has more 'theater' with a nice boost dump noise through the reccirc valve on the stock turbo. Whether high boost/low CR or low boost/high CR gives the best results I have no idea.
I wouldn't go TMIC unless only wanting CGT performance. The heat soak is ridiculous when pushing more power. Remember more power = more under bonnet heat. I have damaged paint near the NACA duct which is heat related. The foam air cleaner needs replacing every two years due to heat damage making it crumble. It gets hot in there. FMIC out front avoids this heat and is exposed to more cooler air at slower speeds than a TMIC
5th injector is never needed to start my motor, ever, its been disconnected since the rebuild. Starts on the button summer or winter, hot or cold.
If continuing to use CiS, consider how its fueled, especially in the mid range. Stock WUR over fuels and saps a little performance in the mid range.
Cam timing has not been mentioned. Just advancing/retarding the cam by a 1/2 to 1 tooth makes a big difference on early or top end boost. I prefer advanced cam and early spooling
Exhaust also needs some consideration to help early spooling and more power. I'm running the ex BassGT custom tapered exhaust.
Compression ratio is the make or break of high(er) boost. I would suggest no more than 8.0:1 CR if you want to go over 1.2bar reliably without octane boosters or meth injection. A series 1 7.5:1 is better for higher boost than 8.5:1 S2 spec. However, stock pistons will not like being pushed too far. They are soft and don't take abuse as well as good forged pistons
A modern 'bat wheel' compressor is the way forward or at least a 2670 wheel as per GTS and 951S. I wish I did this during my rebuild.
Mittlemotor are running #6 turbine housing as there are no #8's out there. They are hitting 395bhp with modified K26 #6, GTS spec CiS etc. and 8.0:1CR and the sparks controlled by their 123ignition dizzy. I believe they run circa 1.4bar+. Its a proven path i would follow if I did it all again. In fact I'd probably buy 100% all their services in building a full GTS motor and ancillaries.
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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
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Mon Jul 24, 2017 10:50 pm Post subject: |
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Carrera RSR, thank you very much for sharing your result/observation/experience, I greatly appreciate it.
| Carrera RSR wrote: | | My front bumper ducted 951 FMIC cools 1.1-3bar circa 6 deg above ambient despite pushing the 2660 6.10 beyond its efficiency. |
I hope my universal FMIC will do as good with the stock S1 turbo K26-2664 G 4.10.
| Carrera RSR wrote: | | 5th injector is never needed to start my motor, ever, its been disconnected since the rebuild. Starts on the button summer or winter, hot or cold. |
Interesting, I知 curious as why you disconnect it? Was it creating any problem?
| Carrera RSR wrote: | | If continuing to use CiS, consider how its fueled, especially in the mid range. Stock WUR over fuels and saps a little performance in the mid range. |
I notice this as well and will have to address this issue. I will have another read at the thread covering this topic.
| Carrera RSR wrote: | | Cam timing has not been mentioned. Just advancing/retarding the cam by a 1/2 to 1 tooth makes a big difference on early or top end boost. I prefer advanced cam and early spooling. |
I致e been back and forward with putting on an adjustable cam gear, but I like/got use to where the boost comes on.
| Carrera RSR wrote: | | Exhaust also needs some consideration to help early spooling and more power. I'm running the ex BassGT custom tapered exhaust. |
Do you have more info on this? Link to the thread?
| Carrera RSR wrote: | | Compression ratio is the make or break of high(er) boost. I would suggest no more than 8.0:1 CR if you want to go over 1.2bar reliably without octane boosters or meth injection. A series 1 7.5:1 is better for higher boost than 8.5:1 S2 spec. However, stock pistons will not like being pushed too far. They are soft and don't take abuse as well as good forged pistons. |
I知 still running stock S1 bottom end and I will not push boost pass 1 bar, if I can reach it safely.
| Carrera RSR wrote: | | A modern 'bat wheel' compressor is the way forward or at least a 2670 wheel as per GTS and 951S. I wish I did this during my rebuild. |
I知 considering the 951S as mentioned by Ideola.
Along with the GTS intake and the FMIC, I知 installing a dual Air Temperature gauge to monitor the pre and post IC air temp. I will dial down the boost back to stock (6-7 psi) and use the pre IC air temp as the maximum air temp I can run post IC. This should keep my on the safe side.
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1980 931S
1981 931 Part car RIP |
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924-76
Joined: 05 Jun 2006
Posts: 1475
Location: Ontario, Canada
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| Posted: Tue Jul 25, 2017 12:54 am Post subject: |
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| 924-76 wrote: | | Carrera RSR wrote: | | Compression ratio is the make or break of high(er) boost. I would suggest no more than 8.0:1 CR if you want to go over 1.2bar reliably without octane boosters or meth injection. A series 1 7.5:1 is better for higher boost than 8.5:1 S2 spec. However, stock pistons will not like being pushed too far. They are soft and don't take abuse as well as good forged pistons. |
I知 still running stock S1 bottom end and I will not push boost pass 1 bar, if I can reach it safely. |
Ref compression ratio, the engine bottom is stock but I'm running a 3 layer MLS head gasket. I can't remember the thickness but I doubt it would raise it above 8.0:1.
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1980 931S
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