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Crotchety Old Bastard
 
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Porsche sized the K27-7200 almost perfictly to match the fueling of 930 CIS fuel head. What is happening with the C2T 3.3 is it dose start to run up against the limits of the turbo. Thus, it can not maintain full boost to red line.

The C2T 3.6 is alread at the limit for the 7200. Adding boost will mostly help in the mid range but there will be little gain up top.

The limit of the K27-7200 is in the 370-380hp range. Again this is about the limit of the fuel head. To deal with this Porsche changed the on boost control pressure that gets a little more fuel for the 3.6.

I would use that simple caluclation as the most just changing boost would get. In most cases losses in effecency will make the gain a percentage of this.

Changing the exaust increasses effecency with not change in boost. This can add HP. Changing the turbo to one with a larger more effecent compressor wheel will see increasses in effecency from not heating the air as much and allow the car to maintain boost higher into the upper RPM range.

The 3.6 if taken to 1 bar is potentally a 400hp motor. However severl things have to be addressed to do this. It needs a turbo cappable of supporting it, it needs a fueling strategy, it needs the restrictive cat to be removed, it may need the intake ports to be opened up a bit.

As to triggering the overboost switch. All WG's tend to overshoot there target at first and then stabilize at there target pressure. They also start to leak boost some before they hit there target level. Some of the electroic boost controlers go through a set up and learn how the WG responds. With this the can keep the WG clamped untill the desired boost level is reached. They also work on the other end to keep it from over shooting.
I have found all of this to be the case as well. You sure you're not an expert?

While adding boost is the cheapest HP it is not the smartest HP. The most efficient bang for the buck on the 965 is to replace the muffler system and then the turbo. These two changes alone transform the experience.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-27-2009, 08:00 AM
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Originally Posted by 911st View Post
I hope you have a fueling strategies as the stock system will not support that level of power.

Playing with some numbers just for fun: A stock 3.6T is 360hp, remove cat/muffler = 380hp. Add boost, 380/1.8 x 2= 422hp. Convert to rwhp, 422 x .85 for drive train loss = 360 rwhp.

Most dynos read differently than the Porsche factory numbers. For example my chipped, cat delete 3.2 pulls 217rwhp which would be 255fwhp.

My maxed C2T with larger IC core, big ports, big exaust, euro head, SC cams... and the K27-7200 pulled about 330 rwhp and would only get to about .92 bar boost. I did not dyno it with the K29 or HF/7006.

380rwhp is 447 fwhp. Very impressive.
The 964 fuel head and system is adequate for up to 400 rwhp not BHP. The fuel head is different for the 964 turbo vs the 930. The 930 will not flow as much fuel as the 964T. There is no way to produce 400 rwhp without changing cams too in a 3.6T. My AFR's are on the rich side especially under WOT she runs a slight bit lean just cruising around and at idle. Nothing I would worry about. If I leaned it out I could get a little more but not worth taking the risk with and I would not use this car on the track set up this way. If iwere to track it i would drop boost down to .85 or .9 bar but for street use you aren't at WOT all that often unless you have a death wish or need to spend some time in the slammer.

The HF K27 really made a difference and I was at 365 RWHP with all the changes and the cat still in place. The cat created way too much back pressure and the car would stumble off the line. IMO removing teh cat is the biggest bang for the buck with these cars.

My 964T will easily keep up with most any new sports car today.

here is a chart of a 3.3l 964 turbo using SC cams, B6 IC, Brian's adjustable WOR and an IA modified fuel head, not sure what turbo he was using my guess K29. AFAIK nothing else was done to it. This car was raced for an entire season under grueling hot conditions without destroying the motor. These are all RWHP numbers. Although i think pushing an engine to this extreme is asking for trouble. When it does go i wouldn't want to be around.



This is a chart from a 3.6T with just 1 bar spring and no other mods with fresh engine. Again these are RWHP #'s I have a lot more like these.

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Gone worth mentioning '71 E '79 SC, '79 built to '74 3.0 RS tribute (2390 # 270 hp), '80 928 euro 5 speed, '74 2.0l 914, '89 944 S2,'04 Cayenne TT '14 boxster, '14 Cayenne GTS many others

Last edited by Cobalt; 02-27-2009 at 08:54 AM..
Old 02-27-2009, 08:33 AM
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Cobalt,

I love dyno charts.

I hope you are right about the 3.6 fuel head. The only difference I could detect was at the WUR that has a lower control pressure on boost than the 3.3.

It is interesting but the factory limminted boost to .9 bar with its special C2T's because of the fuel heads limitations. The limit is not really the head, it is more with the cone profile that the metering plate rides in.

There is a lot more fuel hiding in the stock head. Using an Andial of similar approach to lower control pressure, a reprofiled metering plate to move farther with the higher air flows levels, or triggering the cold running function on the 91-94 turbos that changes the duty cycle on the factory lambda frequency valve at the fuel head are all ways to do so.

On the dyno chart for the 3.3, the AFMs are to lean after 5500rpm. It might be ok on the street. However, not for a track car. If he is short shifting he might get away with if for a while. If he spends much time above 5500, his time will come.

My thoughts and work with a guy back in Colorado (Brent) about five years ago resulted in what is basically the IA head. Mostly it is a head that has been adjusted to be out of adjustment. This can be good for about 10-20% more fuel but it comes at all air flow points. When we first started playing with this we found it made for way to much fuel on first boost. I then proposed using an RPM switch to delay triggering of the WUR enrichment until the point where we needed it. This hurts throttle response by keeping the CP high for longer and slowing down the metering plate but it dose help the fuel curve on first boost.

I ended up taking a different approach with my C2T 3.3. I stepped back to a K27-7200. This limited my top end some but it came in a lot harder and faster. To this I changed how the compressor bypass valve worked to a unit that flowed more an stayed open at steady state rpm and opened immediately with throttle. Lastly I plumped a frequency valve around the WUR and used it to dial in my AFM's at all points and to quickly open the metering plate with acceleration. I may not have had the HP of some but my power under the curve was solid and my throttle response was only matched by an EFI conversion.

Not an expert, must my thoughts.
Old 02-27-2009, 10:17 AM
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Originally Posted by 911st View Post
Cobalt,

I love dyno charts.

I hope you are right about the 3.6 fuel head. The only difference I could detect was at the WUR that has a lower control pressure on boost than the 3.3.

It is interesting but the factory limminted boost to .9 bar with its special C2T's because of the fuel heads limitations. The limit is not really the head, it is more with the cone profile that the metering plate rides in.

There is a lot more fuel hiding in the stock head. Using an Andial of similar approach to lower control pressure, a reprofiled metering plate to move farther with the higher air flows levels, or triggering the cold running function on the 91-94 turbos that changes the duty cycle on the factory lambda frequency valve at the fuel head are all ways to do so.

On the dyno chart for the 3.3, the AFMs are to lean after 5500rpm. It might be ok on the street. However, not for a track car. If he is short shifting he might get away with if for a while. If he spends much time above 5500, his time will come.

My thoughts and work with a guy back in Colorado (Brent) about five years ago resulted in what is basically the IA head. Mostly it is a head that has been adjusted to be out of adjustment. This can be good for about 10-20% more fuel but it comes at all air flow points. When we first started playing with this we found it made for way to much fuel on first boost. I then proposed using an RPM switch to delay triggering of the WUR enrichment until the point where we needed it. This hurts throttle response by keeping the CP high for longer and slowing down the metering plate but it dose help the fuel curve on first boost.

I ended up taking a different approach with my C2T 3.3. I stepped back to a K27-7200. This limited my top end some but it came in a lot harder and faster. To this I changed how the compressor bypass valve worked to a unit that flowed more an stayed open at steady state rpm and opened immediately with throttle. Lastly I plumped a frequency valve around the WUR and used it to dial in my AFM's at all points and to quickly open the metering plate with acceleration. I may not have had the HP of some but my power under the curve was solid and my throttle response was only matched by an EFI conversion.

Not an expert, must my thoughts.
As others said for not being an expert you have sure done a ton of research. There is always so much more to learn.

I have gone over this multiple times with some local shops I have complete faith in and they don't seem to have the concerns that you do about the 964 but totally agree about the 930's. One shop in particular does primarily turbos and have built some serious cars.

I totally agree with the AFR's on the 3.3 and how he survived a season let alone a week with those numbers I have no idea. I would have expected the car to have detonated long ago. Although he might have made adjustments later he never noted them to me. I only posted that chart to show that higher numbers can be achieved although I agree it is way to lean for my comfort zone. But when you think he is getting nearly 535BHP out of a 3.3 on CIS is just crazy but apparently doable although highly risky if not bordering on stupidity.

IIRC after speaking to Stephen at IA some 4-5 years ago, he also felt that the 964 could flow more fuel than the 930 although recommends the fuel head mod. He supplied me with the spring when I purchased the HF K27. All I can go by are the readings I get from my gauges and dyno charts. David's (C2turbo) Inyourfacegauges are very accurate and my AFR's look much different than the 3.3l I posted. .

I don't have the charts on this PC to post otherwise I would, but the readings are similar to the ones for the other 3.6T I posted. Here is the chart of the AFR's and torque. I would be curious to your opinion of these numbers but I think they are relatively consistent with what I want to see to be safe. The problem with the CIS is there is no way to flatten the curve and are limited by how the system is functioning and must make compromises. Although as you can see this particular 3.6 T is making just over 445bhp. I do know this motor did die eventually after many track hours although from what I was told it was a mechanical failure and had nothing to do with fueling issues.

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Gone worth mentioning '71 E '79 SC, '79 built to '74 3.0 RS tribute (2390 # 270 hp), '80 928 euro 5 speed, '74 2.0l 914, '89 944 S2,'04 Cayenne TT '14 boxster, '14 Cayenne GTS many others

Last edited by Cobalt; 02-27-2009 at 11:20 AM..
Old 02-27-2009, 11:16 AM
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Quote:
Originally Posted by Cobalt View Post
As others said for not being an expert you have sure done a ton of research. There is always so much more to learn.

I have gone over this multiple times with some local shops I have complete faith in and they don't seem to have the concerns that you do about the 964 but totally agree about the 930's. One shop in particular does primarily turbos and have built some serious cars.

I totally agree with the AFR's on the 3.3 and how he survived a season let alone a week with those numbers I have no idea. I would have expected the car to have detonated long ago. Although he might have made adjustments later he never noted them to me. I only posted that chart to show that higher numbers can be achieved although I agree it is way to lean for my comfort zone. But when you think he is getting nearly 535BHP out of a 3.3 on CIS is just crazy but apparently doable although highly risky if not bordering on stupidity.

IIRC after speaking to Stephen at IA some 4-5 years ago, he also felt that the 964 could flow more fuel than the 930 although recommends the fuel head mod. He supplied me with the spring when I purchased the HF K27. All I can go by are the readings I get from my gauges and dyno charts. David's (C2turbo) Inyourfacegauges are very accurate and my AFR's look much different than the 3.3l I posted. .

I don't have the charts on this PC to post otherwise I would, but the readings are similar to the ones for the other 3.6T I posted. Here is the chart of the AFR's and torque. I would be curious to your opinion of these numbers but I think they are relatively consistent with what I want to see to be safe. The problem with the CIS is there is no way to flatten the curve and are limited by how the system is functioning and must make compromises. Although as you can see this particular 3.6 T is making just over 445bhp. I do know this motor did die eventually after many track hours although from what I was told it was a mechanical failure and had nothing to do with fueling issues.

Typical boosted CIS fuel curve. With the triggering of boost enrichment it first goes to rich untill the metering plate stalls out. Then the motor has to increass rpm enough to use up the to much fuel to get the AFR's back to something that makes sense. Would be more fun to run a boost controller that would boost higher at low rpms and pull back as the fuel runs out.

A factory stock C2 Turbo's AFR curve is a beautfull thing and near perfict bot pre- and post-boost to red line. Once we turn up the boost the metering plate gets out of the area where the cone around it is calibrated to air flow expectation. It dose not travel very far before it starts to stall. I wonder if the 3.6 made some changes in the cone area.

That cone around the metering plate is like the rpm by air flow map on EFI, or a space cam on MFI. Change the air flow expectations and ya get our of wack.

If I was running a CIS turbo on the track, I would want AFR and EGT readings. Running some race fuel is also a must on a track turbo from what I hear. Again, anyone that runs a CIS turbo on the track without a EGT is playing about $10k or more worth of chicken.

If you have tested your AFR's with a wide band and are and they are good, that is great. I am supprized if it can support 450fwhp with out some fueling help above 5k.

Stephen was a help in my being able to learn about CIS. I used to frequent a Turbo board where we used to hang out and play what if. I am thinking your may have been there to. Back then he and others thought the USA head, lines, and injectors were a limitation and the euro head was the thing. I did not belive this as the cross section of the USA lines though smaller than the euro, still where plenty large for to deliver more than enough fuel with fuel pressure delivery an the spraying full time like CIS dose.

With the IA head came disabling the Lambda function by closing the internal passage and in effect making the USA heads euro heads. I am not a big fan of this as it kills the Lamda function and cold start function on a C2T.

Most do not know this but there even more fuel flow is available from a stock USA head than the IA head by ensuring full travel of the metering plate at upper air flows and playing with the lambda frequency valve which can do the same thing as recalabrating the the euro head dose.

Thinking back to somthing you said earlyer. It sounds like you might be getting a little boost creep with your HF. Though it seems a very acceptable level. This is best watched under full throtle in a higher gear.

Old 02-27-2009, 12:20 PM
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But when you think he is getting nearly 535BHP out of a 3.3 on CIS is just crazy but apparently doable although highly risky if not bordering on stupidity.
I missed this. Where and who is getting 535BHP out of a 3.3 CIS and do you mean at the crank or flywheel?

535fwhp would take about 2 bar boost (almost 30 lbs) on a 3.3 CIS motor and it would need a lot of tricks like huge ports, big cam, extrude hone... to make that kind of power???


435rwhp makes sense.
Old 02-27-2009, 12:39 PM
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435rwhp makes sense.
Sorry, 435fwhp makes sense.
Old 02-27-2009, 12:40 PM
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Originally Posted by 911st View Post
Typical boosted CIS fuel curve. With the triggering of boost enrichment it first goes to rich untill the metering plate stalls out. Then the motor has to increass rpm enough to use up the to much fuel to get the AFR's back to something that makes sense. Would be more fun to run a boost controller that would boost higher at low rpms and pull back as the fuel runs out.

A factory stock C2 Turbo's AFR curve is a beautfull thing and near perfict bot pre- and post-boost to red line. Once we turn up the boost the metering plate gets out of the area where the cone around it is calibrated to air flow expectation. It dose not travel very far before it starts to stall. I wonder if the 3.6 made some changes in the cone area.

That cone around the metering plate is like the rpm by air flow map on EFI, or a space cam on MFI. Change the air flow expectations and ya get our of wack.

If I was running a CIS turbo on the track, I would want AFR and EGT readings. Running some race fuel is also a must on a track turbo from what I hear. Again, anyone that runs a CIS turbo on the track without a EGT is playing about $10k or more worth of chicken.

If you have tested your AFR's with a wide band and are and they are good, that is great. I am supprized if it can support 450fwhp with out some fueling help above 5k.

Stephen was a help in my being able to learn about CIS. I used to frequent a Turbo board where we used to hang out and play what if. I am thinking your may have been there to. Back then he and others thought the USA head, lines, and injectors were a limitation and the euro head was the thing. I did not belive this as the cross section of the USA lines though smaller than the euro, still where plenty large for to deliver more than enough fuel with fuel pressure delivery an the spraying full time like CIS dose.

With the IA head came disabling the Lambda function by closing the internal passage and in effect making the USA heads euro heads. I am not a big fan of this as it kills the Lamda function and cold start function on a C2T.

Most do not know this but there even more fuel flow is available from a stock USA head than the IA head by ensuring full travel of the metering plate at upper air flows and playing with the lambda frequency valve which can do the same thing as recalabrating the the euro head dose.

Thinking back to somthing you said earlyer. It sounds like you might be getting a little boost creep with your HF. Though it seems a very acceptable level. This is best watched under full throtle in a higher gear.

For the record I also monitor my EGT and my I/C temps output side on the street. I enjoy this car too much to take unnecessary risks. I was at the shop I use last night and he said my car will have no problem flowing the fuel I need and the charts and in his case meters don't lie. He never trusts a static dyno test and always straps gauges onto the car to monitor all required parameters under actual real time conditions before he releases if for use. His opinion was if the numbers are good under all load conditions he feels confident that the car is running fine and will stand behind it if something proves otherwise down the line.

I agree messing with CIS is tricky and after several SC's and CIS injected cars I know what can go wrong and have no desire to go there. What I don't understand is why was Porsche so cheap with the CIS system used? My father has a 75 450SL since new using CIS and his fuel head will allow you to adjust each cylinders fuel flow individually. One chance we all take by running higher boost and monitoring parameters at one point is you can have an imbalance in the cylinders and not be aware of it and still show acceptable numbers. Of course many factors come into play. Although it would be nice to be able to test each cylinder or bank of cylinders and make fine adjustments so that no one cylinder is an issue. I figure for the amount I drive this car and that it is not tracked I should be OK, As far as tracking a turbo it is a crap shoot and so much can go wrong if not monitored properly. That is why I am happy beating up on my C2. It is a tough car handles well and is fast enough to have fun and cheap enough not to cry over if something goes wrong.

As far as boost creep the charts I have were done in both 4th and 5th gear and show similar readings. So long as i don't exceed 14.8PSI I think I am OK. Using David's gauges I find that after viewing most spirited drives I am seeing peak boost readings of no more than 14.6 so even less than what i see on the charts although i have seen numbers as high as 14.9 PSI but not very often.
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Gone worth mentioning '71 E '79 SC, '79 built to '74 3.0 RS tribute (2390 # 270 hp), '80 928 euro 5 speed, '74 2.0l 914, '89 944 S2,'04 Cayenne TT '14 boxster, '14 Cayenne GTS many others
Old 02-28-2009, 05:51 AM
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Anthony,

You have a well though out and sorted 3.6 with all the right stuff to ensure safety.

Something I wanted to my 91 C2T was to slip in a set of C2 or C4 normal gears for 2-5. With the tall first in the G50/50 is would make for more of a close ratio set up with less of a drop in RPM between shifts.

I know EFI is the best but I seem to trully enjoy MFI and CIS and how it works. I think the early 930 heads did have adjustably. I do not think I would build a track 930 with out having the head checked for balance. I suspect the damage is more from that side than the unbalanced air flow belief. Air flow in a normally aspirated motor is one thing, pressurized air flow is another. Of course there is nothing wrong with extrude honing a 930 intake manifold for more capacaty and better ballance.

All the best.

Old 02-28-2009, 07:47 AM
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Great information guys, as a newbie to the dark side I'll take all the information I can.

I've been offered a complete Porsche wastegate with a 1 bar spring from a fellow Pelican for about $150. I've found just the spring for about $25.
If the stock exhaust is so free flowing besides the sound and weight savings is there any increase in performance? I've already removed the CAT with the Fabspeed bypass.

Brian
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Old 02-28-2009, 10:34 AM
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