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max boost on K24 7000 question...

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 Post subject: max boost on K24 7000 question...
PostPosted: Tue Jul 26, 2005 6:19 pm 
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Hi folks,

a friend of mine made a dyno run lately with his chipped Audi 200 quattro.
It´s an MC2 engine with single pass IC, K24 & MAC 14.
ECU was upgraded to 2.5bar absolute boost pressure (CIS still on-board), POV fitted, catalyst removed.
The engine develops 400NM of torque @ ~ 3100/rpm.

Now comes the problem.

Power curve nicely ramps up to 4500 RPM, but suddenly drops with some smoke from the end pipe. Max hp output was 220hp @ 4800/min - obviously not what we were looking for :(

What happened there?

To much boost?

After the dyno, engine runs fine with no signs of possible breakdown.

I´m running almost the same setup on my MC2 except for the POV (will be fitted soon). Car runs fine with max boost up to 2.3bar (absolute) without engine light coming on.

Does this mean, we reach the boost limit of the stock K24 at 2.4bar or could there be another problem?

Any suggestions welcome.

Cheers,
Olli

ps. here´s the dyno snapshot from my friend´s car


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PostPosted: Tue Jul 26, 2005 7:01 pm 
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Well, I didn't think any K24 would support much more than ~18psi, and unless your CIS tuner is really good, it can't either. Could explain the 2.3bar limit (~1.3bar boost).

Chassis dyno's also aren't that friendly to engines, especially when you start stressing stock components that need a LOT of cooling. That setup usually does better on the street where it can get the air flow it needs.

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PostPosted: Tue Jul 26, 2005 10:10 pm 
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k24's are about all done over 18psi. slight torque increase from there, but no speakable HP. you've hit the limit!

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 Post subject: Ahh.. thank you guys!
PostPosted: Wed Jul 27, 2005 2:12 am 
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Well,

we had a very large cooling fan in front of the car during the dyno run.

The max CIS duty cycle was programmed to 95% (the absolute possible maximum). Idle mixture was set to 55-60% duty cycle. Fuel pump & relay were renewed shortly before.

But i think you guys are right - we hit the CIS & K24 (boost) limit, if i read the compressor map correctly.
Like i said, up to 1.3bar everything works fine - with 1.5 on higher RPMs you end up with some slight hesitation & sometimes the engine warning light coming on.

So we better back off boost a little bit...

BTW, 1.3bar is still enough to out-perform a Porsche Cayenne S between 120km/h - 200km/h on the Autobahn... :D

Cheers,
Olli


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PostPosted: Wed Jul 27, 2005 6:30 am 
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The CEL is even coming on? You guys are probably knocking like crazy and the computer can't retard the timing enough to stop it. Has the ECU been properly remapped with a complete timing map? If not there's no point in trying crank up silly amount of boost, you'll run into knock in no-time. The stock ECU's timing map stops retarding at .6bar.

And you _are_ monitoring your air/fuel ratios so you have an idea of whats going on on the dyno... right? ;)

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PostPosted: Wed Jul 27, 2005 7:03 am 
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Newt,

the ECU is well remapped completely with new timing, boost & fuel maps. The programmer did monitor parameters like EGT, AFR (Lambda) & boost very well on a Laptop. I know this, since i was the driver during that particular test run (which took place a year ago or so).

I have a older version of that chip available as bin. data. The old one was mapped for 1.75bar absolute & cut-off @ 2.0bar.

I´ll add these data at the attachment

The dyno run was performed with the newer 1.95bar upgrade w/o fuel pump cutoff.
However, we have a lot of guys here, where this setup works fine as long as you don´t exceed 2.3-2.4bar absolute.
And this was the reason for my question above.

Conclusion: K24 should not exceed 2.2-2.3bar (18psi).

In other words: what we did on the dyno, was finding the limit of this setup.

I´m totally aware of your words, regarding remapping the ECU & especially the timing.

Thanks,
Olli


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File comment: 1.7bar MAC 14 ECU upgrade - open with Win Hex...
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PostPosted: Wed Jul 27, 2005 7:08 am 
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gotcha, just checkin the basics :)

Did you pull the codes afterwards to check the reason you got a CEL? It could be something as simple as a bum knock sensor or intake air temp sensor yanking back the timing. If all your EGT's and A/F readings looked good.

Other than that you're probably spot on, sounds like you're just exceeding the turbo effiency range and turning it into a furnace, probably heating the air and causing the knock/cel dealio.

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PostPosted: Wed Jul 27, 2005 7:25 am 
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Yeah Newt,

i did pull the codes - both knock sensors came on, complaining that knock regulation range was "overboosted" - much what i expected.
So timing was at it´s very end of retard range, but still knocking.
Way too much boost...

There were no other fault codes & all components were checked before.

I guess your last sentence hit the point perfectly.

Cheers,
Olli

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PostPosted: Sat Aug 20, 2005 11:18 am 
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Hi

Typical power curve for CIS apart from the very good torque level.
My 88 URQ with K26 turbo at 1bar boost will produce a similar power curve that also goes flat after 4500RPM produces 212BHP on my local dyno
K24's will flow enough air to hit 290BHP on chipped S2's so it's not the K24 stopping the power curve from rising after 4500 although the heat produced by the small turbo will not help you on a dyno run.
An EFI(lumenition in this case) modded 88URQ running at only 1 bar will produce about 245-250BHP most of this is made after 4500rpm as the power curve just keeps rising to 6000rpm.
I think if you want more power(not torque) you will need to bin the CIS keep the K24 and go EFI
Regards.

Mark


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PostPosted: Sat Aug 20, 2005 11:30 am 
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really think that a 10v 200 k24 is the same as a 20v k24 ? come on. yes, the 10v k24 IS at its limit. you need more turbo, and less knock too.


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PostPosted: Sat Aug 20, 2005 12:12 pm 
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No, but they are very similar....

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PostPosted: Sat Aug 20, 2005 12:24 pm 
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Hi

I must admit I'm not sure of the slight differences of the K24's on the total KKK range but as far as I'm aware they are the same or very similar for the 200 and S2

See http://www.sjmautotechnik.com/trouble_s ... oparts.htm

200TQ and S4/S6(5cyl) listed as the same, I'm guessing the the S2 will also be the same.

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PostPosted: Sat Aug 20, 2005 12:43 pm 
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Yes, they are the same - apart from the small pressure tap for the WGFV, the 20V turbo has and the 10V is missing.
All others remain absolutely the same.

I think, if you back up the boost a little bit down to ~ 1.2-1.3bar, you´ll be fine and ignition will be within it´s range.

I removed the 3mm WG shim on my car and now, the boost will not go beyond 1.3bar @ 5th gear.
The car now runs much better on hi revs, without those slight hesitations, typical for a retarded timing.
Sometimes less is more...

I think the higher power O/P on the 20V is mostly caused by higher rev limits + the much larger twin exhaust. You can really feel the back pressure on the 10V, resulted by the exhaust...
...and feel the difference, when your DP to Cat bolts come loose or when there is no Cat at all :)

Well, we keep on testing...

Cheers,
Olli

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PostPosted: Sat Aug 20, 2005 1:16 pm 
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Hi Olli

When Tresser modded the URq's they changed the metering head I believe to a larger 8 port version(obviously blocking off the other ports!) these were meant to make about 250BHP.
The one piece manifold will restrict the power apparently to about 250BHP- options are Dialynx manfold(straight fit retaining (CIS) or tubular (no room for CIS).
On a 10v URQ std exhaust(no cats in the UK for 10v) is not a problem until about 350 ish when 3" bore is better. Don't know how the URQ and 200T exhausts compare though.
Water injection will help a lot with high boost levels and inlet charge temperature.

Good luck with the project

Regards
Mark


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PostPosted: Sat Aug 20, 2005 1:36 pm 
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Olli W. wrote:
I think the higher power O/P on the 20V is mostly caused by higher rev limits + the much larger twin exhaust. You can really feel the back pressure on the 10V, resulted by the exhaust...
...and feel the difference, when your DP to Cat bolts come loose or when there is no Cat at all :)


I think that it's the 10vt that really hate backpressure, they really respond well to a LARGE free flowing filter too.


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PostPosted: Sat Aug 20, 2005 3:35 pm 
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The only difference between 10v k24's and 20v k24's can be the bearing size used in the turbo. It's either 14 or 19mm. as a guy on audiworld is finding out right now, the rebuild kits are only available(or so it seems) for the 19's. which are the same as a k26. I believe the wheels are the same from one to the other.

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PostPosted: Sat Aug 20, 2005 5:28 pm 
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OK maybe I'm chiming in a little late. But here's my two cents, but I got a lot of documenting and dyno time behind it.

CIS with a chipped mc-1 and a K24 goes really lean after 15 psi and 4500 rpm. Turbo can maintain about 17psi to redline and that's about it.

Now let's say fuel is no problem through your CIS system. (which is way more involved than just chipping it and upping the fuel duty cycle)
With my boost controller I can hit 28 psi 3700-4500 rpm then it falls fast leveling out at 17 psi. Which concurs with my HP numbers on the dyno.
209whp with 15psi... 211whp with 21. The only benefit in having the boost any higher than 18 psi is the extra TQ in the rpm area where the turbo can still pressurize higher levels. Which was more than obvous in my dyno's. 190wtq at 15 psi 255wtq at 21.

My A/R was below 10 at peak torque and at 12.2 5-6k rpm's

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PostPosted: Sat Aug 20, 2005 6:20 pm 
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i thought i saw some numbers showing they were not the same. anyway, logic dictates that they are not..mc1=165hp with k26 , mc2=165 with k24...think they would use a smaller flowing turbo than they did on the mc1 to make 227hp on the s4? not to mention you can feel an mc1 more eager to make hp than an mc2 above 225hp which is right where the stock s4 is rated. and sure the s4 makes bigger hp numbers because it revs higher, but it takes a turbo with more flow to make 18psi @7000rpm than 18psi @6400 on 2 engines of the same size.
at least the knock sensors did their job, (a better job than any ones ear) that is why i like them. still, messing with old turbo audis is the best, and 10valves are still cool and a great power plant.

my .02...but, i could be wrong


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PostPosted: Sun Aug 21, 2005 10:47 am 
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Quote:
When Tresser modded the URq's they changed the metering head I believe to a larger 8 port version(obviously blocking off the other ports!) these were meant to make about 250BHP.


Yes, but that involves quite a lot R&D finding the right one.
And at that time, Treser (like all the other tuners) were far apart from having the computer power in order to program the ECU properly. Further more, the old KG engine doesn´t have a chip nor the parameters to program any boost/fuel/etc...

Quote:
The one piece manifold will restrict the power apparently to about 250BHP- options are Dialynx manfold(straight fit retaining (CIS) or tubular (no room for CIS).


I already have the two piece EM and so does the guy mentioned above.
Though still not the optimum in flow, the 2p has a much better and slightly larger design, resulting in (slightly) improved performance.
Dialynx was never an option for me, since it is inferior to the Audi 2p EM.

Exhaust restriction IS a real problem on the 10VT on top end.
We had one guy here in Germany running 300hp with original CIS still in place, no Cat & 3" exhaust from DP on. Turbo was a K27 as far as i remember.
Conclusion: a larger exhaust is a must if going beyond ~ 230hp. EM is good for more (~ 300hp).
Remove the Cat and test drive - this is nothing else than having a larger exhaust.

I don´t think, that the CIS will be completely topped out at 230hp.
Can anyone confirm or deny this?
The programmer did measure the AFR very well when doing the chip upgrade and it was still in range - at least at 2.0bar absolute pressure.

Cheers,
Olli

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PostPosted: Sun Aug 21, 2005 12:46 pm 
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pkw wrote:
i thought i saw some numbers showing they were not the same. anyway, logic dictates that they are not..mc1=165hp with k26 , mc2=165 with k24...think they would use a smaller flowing turbo than they did on the mc1 to make 227hp on the s4? not to mention you can feel an mc1 more eager to make hp than an mc2 above 225hp which is right where the stock s4 is rated. and sure the s4 makes bigger hp numbers because it revs higher, but it takes a turbo with more flow to make 18psi @7000rpm than 18psi @6400 on 2 engines of the same size.
at least the knock sensors did their job, (a better job than any ones ear) that is why i like them. still, messing with old turbo audis is the best, and 10valves are still cool and a great power plant.

my .02...but, i could be wrong


You cannot use logic to determine differences between turbos used on engines with very significant differences in key areas.

The 3B and AAN are better every area that effects volumetric efficiency than any 10v, add to that the increase in boost level and you have the explaination for the increased power. The 500 rpm increase in "factory" rev limit is a side benefit of the breathing improvements.

As for the K24...while its true that it's smaller than the K26 used on the MC1 its also a much more efficient design and doesn't give up much in peak capability. It also has an advatange of spooling very quickly, something quite important when you need torque to accelerate an overweight S-car.

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PostPosted: Sun Aug 21, 2005 6:01 pm 
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cr is the easy way to get ve improvements and when cr is increased,what you are saying is true of ve improvements- when cr derived ve improves you do not need more flow to make more hp. lets be reasonable, gains in cr ve are only going to help by about 10 percent tops.....so, of course the s4 breaths better and that is why it needs a turbo with more air flow to feed it. lets take this example to the Nth degree. put a k24 turbo on a viper with 500hp. the turbo could not add anything to the peak hp figure because it would be out of its range before it can make an air flow increase above that 500hp level. the turbo would over-spin with the viper still being in vacuum. could be the same turbo, i just doubt it. (edited to make it clear i was talking of cr increase)


Last edited by pkw on Mon Aug 22, 2005 8:01 am, edited 1 time in total.

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PostPosted: Sun Aug 21, 2005 7:31 pm 
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The K26 and K24 that Audi used have pretty similar maps going from memory. The K26 is like 73% efficient, and te K24 is like 74%. The K26 has a higher PR limit, but I thought narrower range between the air flow limits. I'll have to look at the maps again some time.

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PostPosted: Sun Aug 21, 2005 7:42 pm 
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here is an idea.... instead of everyone arguing if the k24 on a 10v or a k24 on a 20v flows more... how about this.... EVEN IF THE K24 ON THE 20V FLOWS MORE, IT IS STILL A TINY RESTRICTIVE TURBO, WHO'S SOUL PURPOSE IS TO INCREASE LOW END TORQUE. am i right? extremely fast spooling little turbo... instead of a larger more flow capable one...

secondly, exhaust backpressure from the smaller turbine...

now i think we can agree if we want more hp, you cannot look only at intake flow, and boost.. you need to look at exhaust backpressure, intake temps, ect.

forcing a k24 to 18 lbs boost is stupidly inefficient, even if we intercool it and get the intake temps to sub 150F we still are dealing with a huge pressure differential and loss of flow upfront at the turbo.

so the solution to your problem is get a better flowing turbo.

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PostPosted: Sun Aug 21, 2005 8:05 pm 
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so the k24 is small. it's a great street turbo. good for a nice area under the curve dyno chart. driveability is great from it.

So how come everyone assumes that the 2 piece or going full tubular/efi is the only options for exhaust manifolds? I can't believe no on has done a log header just to get better than stock flow, and not have to take the dive into EFI. They are cheap/easy to build. there's a guy here who'll build em for $200 all day for stock turbo fitment/location.

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PostPosted: Sun Aug 21, 2005 8:10 pm 
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i made a log header, i nearly finished it but i gave up when i got my tubular header.... i suppose i just stopped caring at that point... LOL

yes a log can flow good and be much better then stock, but if your going to spend money, dont screw around and just go to tubular...

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