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Bigger Turbo, leaner AFRs!

Hello all,

Last week I replaced the stock 7200 turbo on my 1991 3,3l 965 with a bigger hotside 7006 turbo.
Result: boost now kicks in slightly later but with a bigger punch!

So far so good, I also checked my AFRs at WOT with my PLX inyourfacegauge just to make sure the mixture isnt too lean.

BEFORE with the stock turbo I saw very low 10 AFRs for a looong time in midrange (accelerating from 2000rpm), very slowly increasing to low 11s and finally high 11 AFR as rpms rise, simply too fat!
Idle and cruise AFRs were around 14,5-14,7.

Now with the bigger turbo I see 10,8 AFR in midrange MAXIMUM and only very short, rising up to 11,5-12,0AFR, same boost as before, 0,95bar.
Idle and cruise AFRs are the same.

I didnt expect this positive side effect, now the overfat midrange is almost gone because this new turbo simply pushes more air with the same boost!

I was about ordering a Digi-WUR to get rid of the low 10s in midrange but might aswell just leave it as it is now!

Performance is very well and I think there is still enough fuel to raise the boost a bit, maybe an additional 0,1bar.

Car is 965 with Euro fuelhead.

What do you guys think?


Old 03-31-2009, 03:54 PM
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Yea, thats the name of that tune. Using different volume of air push is one good way to change your AFR. Sort of different than what some do but if you can figure it out before hand, it can solve certain situations. Congratulations on getting lucky, or did you think this would be the outcome? I recently exchanged turbos on two 930s as one was overboosting by .2 bar and the other was getting too little air to fill up the enlarged ports and air space. They both run much better now. One was over boosting to 1.4bar between shifts and the other was filling up at .08. Now one is 1.2 bar and the other at just over 1.0 bar. AFR.s both @ around a safe 11.8 at their max. I only give full throttle from 4500 RPM to 7000 RPM as that is where the cams work.
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Last edited by voitureltd; 03-31-2009 at 04:43 PM..
Old 03-31-2009, 04:28 PM
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PM sent.-interested in the old 7200.
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Old 03-31-2009, 04:28 PM
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I also run with a K27 7006 and just last weekend finished installing my LC-1 AFR gauge...along with an adjustable WUR courtesy of Brian Leask. Brian pre-set the control pressures based on my modifications and the boost I run at.

So, the first run out the door...boost control set at .8bar, steady state crusing with no boost had the AFR's right at 14.0. I could probably lean her out just a hair, but it's close enough to stoicheometric. Full boost had it richer than needed....10.5. Oh...I forgot...I also installed a simple solenoid and MSD rpm activated switch set to open at 3200 (way too low, but that's where I started just to safely make sure it was working).

Next, back in the shop, I dialed up the boost to .9 bar (which is where I intend to run most of the time, or up to 1.0 when the mood strikes me) and put a 4200 rpm chip in the MSD (to delay boost enrichment until then). Out for a spirited blast and the full .9bar boost AFR settled in from 11.8 to 12.0. At about halfway through the boost build (say around .5bar) I'm seeing AFR's dropping to around 13, then continuing on down as rpm's build and the WUR starts enriching.

If this helps, my control pressures are as follows: COLD: 2.0, WARM 3.75, enrichment 2.5. Still have some tuning to do, but overall I'm happy with it. Need to hook up my laptop in the car and see if I can figure out how to map everything.

To get rid of your fat midrange, try installing as I have done the rpm switch/solenoid on pressure feed line to the WUR. You can buy the complete setup from Brian (and you will get nothing but extreme quality workmanship and support), or source the parts yourself as I did.
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Old 03-31-2009, 08:00 PM
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It doesn't quite work that way. Turbo sucks trough barn door so CIS doesn't know/care about turbo efficiency. It just dispatches fuel according to air inhaled.

I believe you raised AFR's by new turbo "missing" to hit the fat range by developing boost later. also, you might have corrected previous boost leak which might have contributed to overrich condition.

Better efficiency will develop more power though. So will "less fat" AFR's.
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Old 04-01-2009, 12:41 AM
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Quote:
Originally Posted by beepbeep View Post
It doesn't quite work that way. Turbo sucks trough barn door so CIS doesn't know/care about turbo efficiency. It just dispatches fuel according to air inhaled.

I believe you raised AFR's by new turbo "missing" to hit the fat range by developing boost later. also, you might have corrected previous boost leak which might have contributed to overrich condition.

Better efficiency will develop more power though. So will "less fat" AFR's.
Boost now kicks in a little later thats correct, with headers and decat I see boost around 300rpm later now compared to the 7200.

Thinking of boost leak, how could I have fixed a boost leak by just changing the turbo? I didnt touch the intake or took off the intercooler. Just took off the rear bumper and swapped the turbos... left L shaped inlet pipe was tight aswell as hose to intercooler. Car ran great with the 7200 stock turbo apart from the typical too rich condition.

Maybe the car is not running pig rich in midrange now because the boost kicks in later, but it is really not a big difference compared to stock, just a slight moment later.
Performancewise with the 7006 it is far better than before, absolute digital powerdelivery, thats what I like! First almost nothing, then all!!

As far as I know the stock WUR starts to enrich when it sees a certain amount of boost, the 7006 spools later so the fat midrange almost got deleted, could this be the cause? Before I saw low to mid 10s up to 4400rpm, now only 10,8 very short and after that mid to high 11s.

It wasnt my intention to cure the fat AFRs by swapping the turbos, I just wanted some more punch up top thats why I took the 7006. But I really like what my AFR gauge is telling me since the new turbo is installed.

Here is a video of my AFR gauge with the stock turbo installed:

http://www.youtube.com/watch?v=wINZmmarzsw

You can see the 10s for quite a while up to 4300-4400rpm.
It is not the best video because I used the 2nd gear, 3rd or 4th starting from 2000rpm would have been better.

I am not selling my stock 7200 turbo btw, but might change my mind in the near future and will let you know, thanks for the PMs and for your interest.


Last edited by gogomobil; 04-01-2009 at 02:07 AM..
Old 04-01-2009, 02:00 AM
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[QUOTEAs far as I know the stock WUR starts to enrich when it sees a certain amount of boost[/QUOTE]

If my memory serves me right, the WUR starts enriching at very little pressure, like .3 to .4 bar. That's why with updated turbos (well, for those of us that started with the old 3LDZ, the K27's are an update) the earlier onset of boost has the WUR fully enriching wayyyy before you have built enough rpms. As already mentioned here, the 7006 does come on later than the 7200, and may have been all you needed to flatten things out a bit.
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Old 04-01-2009, 07:13 AM
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Quote:
Originally Posted by gogomobil View Post
Here is a video of my AFR gauge with the stock turbo installed:

http://www.youtube.com/watch?v=wINZmmarzsw
Nice video and great sound! I wouldn't dare to pull so many revs. Max power is around 5500 RPM and (if rest is stock) you still have those Carrera rod bolts that don't like hi revs
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Old 04-01-2009, 08:53 AM
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Greetings:
I just picked up my car last week after 9yrs of not driving it..., 911SC Targa-915-with a 3.3turbo-SCcams-7006turbo-MSD 6AL-& COIL.Magnecor wires, b&b dual exhaust , modified air-intake..HKS-FUEL Enrcihment..

1ST impressions --on the straightaway streets slow.....YEP--Slow i was so upset and felt like an anchor was holding on.......I was freakin upset....The car coughing dying for air....etc....NO BOOST was showing.....etc...etc...

My mechanic told me give him the keys...
ALL I KNOW--when he drove it, while i was watching....i heard the turbo spool up and burlble on the long run....

When he came back....He said,,"YOU HAVE STEP INTO IT"!...Don't be shy.....Gotta break her in.....

Once on the highway....I KNOW WHAT THE HECK HE WAS TALKING ABOUT..

I missed that feeling for a long time..............I hope i will never go thru a long stint of not driving a porsche turbo.....ITS A SIN!!!!

Once home....I shut her down...And started her up within a min.--just to see if it will start....(my luck in the past the car got hot and would not start). Now theFuel accum. changed,plugs ngkracing,msd...all in...IN A SEC..SHE FIRED UP...
I AM HAPPY!!!!!
I am currently in SC-charleston--for next 7 weeks for training...SO--NO CAR...

The 7006-turbo---HAS TOP END.....LUV IT!

ENJOY!
Old 04-01-2009, 12:49 PM
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Thanks for the input guys, for now I will leave it like it is, I am happy with the performance and the added bonus of improved AFRs @ midrange.

@Goran,

Thanks, the only reason I rev it so high in the video is the sound
Old 04-01-2009, 01:56 PM
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Quote:
Originally Posted by gogomobil View Post
Thanks for the input guys, for now I will leave it like it is, I am happy with the performance and the added bonus of improved AFRs @ midrange.

@Goran,

Thanks, the only reason I rev it so high in the video is the sound
The next sound you hear might not be the one you want to hear.

Wait till you try another, more efficient and modern turbo - the 7600 will feel like a dinosaur.
Old 04-01-2009, 04:26 PM
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The next sound you hear might not be the one you want to hear.

Wait till you try another, more efficient and modern turbo - the 7600 will feel like a dinosaur.
I like to rev it to redline and if it blows, it blows.
My boost is not excessively high with 0,9-0,95bar and 965 intercooler.
AFRs are spot on.
These engines are very solid and you should be able to drive WOT all day long on the Autobahn without speedlimit, thats what they are made for (I live in germany).

Regarding the turbo, I like the off/on power delivery of the 7006, and this turbo also doesnt loose its punch @ higher rpms. If I wanted my car to feel like a big displacement N/A engine, I would have bought a Garrett or a HFS.

Last edited by gogomobil; 04-02-2009 at 03:32 AM..
Old 04-02-2009, 02:15 AM
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Quote:
Originally Posted by gogomobil View Post
I like to rev it to redline and if it blows, it blows.
My boost is not excessively high with 0,9-0,95bar and 965 intercooler.
AFRs are spot on.
These engines are very solid and you should be able to drive WOT all day long on the Autobahn without speedlimit, thats what they are made for (I live in germany).

Regarding the turbo, I like the off/on power delivery of the 7006, and this turbo also doesnt loose its punch @ higher rpms. If I wanted my car to feel like a big displacement N/A engine, I would have bought a Garrett or a HFS.
The manual says "max permitted RPM" is 6500 RPM and "max temporary RPM" 7000 RPM.

Engine is indeed solid and will allow full speed all day long but at lower revs. Running it "all day" at 6800 RPM is 300 RPM above max permitted RPM and might stretch the rod bolts. Piston acceleration forces are proportional to >square< of engine speed, so forces pile up quickly.

Enjoy your motoring,

Regards
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Old 04-02-2009, 03:39 AM
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Originally Posted by beepbeep View Post
The manual says "max permitted RPM" is 6500 RPM and "max temporary RPM" 7000 RPM.

Engine is indeed solid and will allow full speed all day long but at lower revs. Running it "all day" at 6800 RPM is 300 RPM above max permitted RPM and might stretch the rod bolts. Piston acceleration forces are proportional to >square< of engine speed, so forces pile up quickly.

Enjoy your motoring,

Regards
Thanks Goran.
my revlimiter kicks in @6500rpm.
Old 04-02-2009, 03:50 AM
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Just wondering if you truely have those AFRs.
Most WBO2s are very sensitive to pressure (and heat), and the change in turbo could make that happen. If the WBO2 is at the typical point (about 4 inches before the turbo) then you maybe getting biased readings like i did with my K27HF/GHL combo. I had a Rice FE module and it seemed to be performing too well. I removed it and found that there was no change. After relocating the WB02 in the tail pipe my lowest AFR (10.5) changed to 13.9AFR. Be careful. I was told that the best location for the WBO2 is after the turbo (providing the muffler has low flow restriction).
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Old 04-02-2009, 05:41 AM
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Interesting,

My 94 turbo I switched to one of Kevin's K27 HF turbos and found I get all the air I need up top along with quicker spool up and far more responsive throttle control. I have one of David's InYourFaceGauges mounted in my tach. You can see how the sesnsors are located in the picture.

I am seeing very good AFR's. If I am lugging it around town and punch it in any gear at around 3k rpm's, AFR's go from 14.5 down to 10.0 and will gradually climb to a solid 12.0. by around 4500 rpms. If I down shift and punch it I see immediate 11.5 and a solid 12.0-12.5 up to redline.

I am running a 1 bar spring stock fuel head and WUR. I normally record around 14.3 to 14.5 PSI with a very occasional 15.0 which is a tad more than I like. I might drop to a 9.0 spring or a boost controller.
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Old 04-02-2009, 06:45 AM
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Anthony:
I just had another thought:
I am curious, what did you do to drive the O2 input to the Lamda-Jetronic on you 94 CIS control? Did you also use the stock O2 sensor in the regular 'bung' of the headers? Just wondering, because if you are still running the 94 CIS electronics, i am wondering how the AFR is ending up to be 14.5 without much load. I found if i removed my 02 (on 89 CIS), it dropped the AFR to around 13.9ish at idle (does not work for CA emissions). If you are running the stock O2, then that would explain things, because starting in 89 (i think), porsche added a enrichment module to the CIS control (similar to the Andial enrichment - so to speak). I found that with the CIS operating from 02, and WO2 sensor in the tail pipe (temporary), the AFR range reduced from 14.0- 10.5 (read with WO2 in O2 location, and O2 to jectronic removed) to (14.5-12.5 with WO2 located inside the tailpipe, with O2 for jectronic active). So maybe it wasnt actually the location of the O2 sensor, but the effect of the jetronic fuel enrichment taking control.
Does anyone know more about this? (I cant do anymore comparisions now because i am fully electronic (aftermarket EMS)).
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Old 04-02-2009, 07:02 AM
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Quote:
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Anthony:
I just had another thought:
I am curious, what did you do to drive the O2 input to the Lamda-Jetronic on you 94 CIS control? Did you also use the stock O2 sensor in the regular 'bung' of the headers? Just wondering, because if you are still running the 94 CIS electronics, i am wondering how the AFR is ending up to be 14.5 without much load. I found if i removed my 02 (on 89 CIS), it dropped the AFR to around 13.9ish at idle (does not work for CA emissions). If you are running the stock O2, then that would explain things, because starting in 89 (i think), porsche added a enrichment module to the CIS control (similar to the Andial enrichment - so to speak). I found that with the CIS operating from 02, and WO2 sensor in the tail pipe (temporary), the AFR range reduced from 14.0- 10.5 (read with WO2 in O2 location, and O2 to jectronic removed) to (14.5-12.5 with WO2 located inside the tailpipe, with O2 for jectronic active). So maybe it wasnt actually the location of the O2 sensor, but the effect of the jetronic fuel enrichment taking control.
Does anyone know more about this? (I cant do anymore comparisions now because i am fully electronic (aftermarket EMS)).
Good Point. The O2 input to the Lamda-jetronic is still in the regular bung of the B&B headers.

Not sure what changes were made to the CIS and when. My experience is with early SC's and the 94 turbo only. Although IIRC the 94 3.6T was fitted with a different fuel head chamber design, I believe there is also a different Oxygen control sensor used. AFAIK the 3.6T oxygen sensor control unit does not process the 0 degree throttle switch position to improve pickup in the low load range. There is also a difference in the acceleration enrichment device but I don't know the differences from memory.
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Old 04-02-2009, 07:41 AM
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Quote:
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Just wondering if you truely have those AFRs.
Most WBO2s are very sensitive to pressure (and heat), and the change in turbo could make that happen. If the WBO2 is at the typical point (about 4 inches before the turbo) then you maybe getting biased readings like i did with my K27HF/GHL combo. I had a Rice FE module and it seemed to be performing too well. I removed it and found that there was no change. After relocating the WB02 in the tail pipe my lowest AFR (10.5) changed to 13.9AFR. Be careful. I was told that the best location for the WBO2 is after the turbo (providing the muffler has low flow restriction).

I have the same o2 sensor like cobalt, PLX Devices from inyourfacegauges.
This sensor is very accurate and needs no calibration at all. My sensor is not 4 inches before the turbo btw. My car has been on the dyno twice and the dyno AFR showed the same numbers, the PLX sensor reacted quicker than the dyno AFR sensor, that was the only difference. The AFRs are almost the same after the turbo swap but without the very fat midrange. I deleted the stock lambda control and set idle AFR manually to around 14,7, that was all I did. I run headers and cat delete too.

Thank you for your time,

gogo
Old 04-02-2009, 01:32 PM
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I'm told any AFR sensor should be fitted after the turbo but before the muffler, back pressure will give bogus readings in front of the turbo, not sure if this is to do with the wastegate? 3 or 4" after the turbo is supposed to be optimal, and always at a 12 O'Clock position, as if it is fitted at the bottom (6 O'Clock position) it will get fouled up

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Old 04-02-2009, 03:38 PM
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