Best CIS engine performance combo

[djdawson2]

Gents,
Been reading the list, talking to a few folks, and have heard some very helpful input. I've also received some ideas from RarlyL8 (Brian) that has been beneficial.

My goals are probably very "normal" as I'm looking for nice power starting no later than 3k rpm and pulling to 7k rpm with out running out of air. I intend to keep the CIS intact, as I live at nearly 9000 feet, and can be down under 5000 feet or over 10000 feet within a half hour. I feel I must keep the flexibility of the CIS to adapt to such altitude changes.

I don't really have a target horsepower figure... but I would like the project to result in a car that could turn in low 12s in the 1/4 mile. I've been spoiled by several Audis I've played with, as they have all been capable of 12 second sprints... and my 930 just feels very slow right now

I like the idea of the SSI exchangers, Y-pipe and muffler that Brian has suggested... but I'm debating on which hairdryer to select. One of my Audis (a 2.2 5 cyl) makes 442 whp using a GT30R (3076) Garrett. It would seem that that turbo on a 3.3 would hit hard at a very low rpm, and be capable of delivering through redline. Anyone with experience with this turbo?

Also, I've read with GREAT interest some of the chat in the digital WUR thread (tome?). It seems this would be worth buying in to, if there is actually a completed project. Is this product really available yet?

OK... please tell me what you'd do with a bone stock CIS car given the chance. Oh, and the A/C must stay.

Thanks!

[krasuskyp]

...and so it begins...

MUWHAHAHAHAHaaaaa

8-)

well now THAT didn't take long heh heh. Looking forward to this Dave. Madman.



ps. I hear you on the 930 feeling slow (stock of course)
pps. A/C schmaycee heh heh

[RarlyL8]

The GT30R and K27HF are both used in this application. I have never done a direct comparison of the two because they are set up totally different. The flanges are not the same and if memory serves the oiling requirements are different as well.
I've had the blessing of having my way with a few bone stock cars, low 12's can be done with bolt-ons alone.

[911st]

What year. What exaust.

Your goal seems to be reduced lag and a fuller mid range.

My two cents.

The basics are turbo, Intercooler, exaust, & boost.

Had a frend build a Turbo up your way. Need a bigger turbo because of the altitude but he was running cams, big boost (1.1 bar).

A K27-7200 on his car was not enough and might not get you past 350fwhp. However, you might want to look at depending on your goals. It comes in fast and hard and can be a lot of fun. The big turbos tend to start to come on a bit earlyer but reach full boost later. More civilized but cary boost to red line.

I asunm you have a later USA / Euro style heat exchanger system. If not this must be corrected. The Euro Style is not a bad system and dose not limit making power, just not the best it could be as to volunm and response.

If you just have a bunch of money burning a hole in your pocket or are intent on headers, check in with M&K Exaust about there modified 993 eat exchangers. Probably the best set up with heat to date.

Because of your altitude the turbo is probably the first thing on the list. Increased effency will add hp.

With this a low back pressure muffer section. This will alow the turbo to spool faster and make about 15 more hp. You might be happy with just these mods for a while. If it is cool most of the time there could even change the boost spring out for a .9bar.

Then a larger intercooler. Free HP. Good for about 30-35hp at the same boost level.

With the IC .9 bar boost spring is a save boost even on the track. Adds about 15hp. 1 bar is for another 15hp. Everyone seems to want tgo go to 1 bar but to me the power v risk pay off is not there with todays gas.

Now look at larger intake ports and C2 or SC style cams timed for low end (need sport valve springs). If you want better pre boost response, can change the pistons out to 8/1's and lower the boost back down.

I used to be a fan of the SSI. I do not think I would do them unless my stratagy was to maximize pre boost operation with 8/1 compression pistons. The length and smaller dimater tubes might work against upper HP and the increased volunm of a long tube header design should also work against boost response.

Now the tuning.

For safty verify the fuel deliver is ballanced at each injector. If not you might think you are pulling 12.1 AFR but have one cylinder running 13.5/1.

Get it on the dyno and check the AFR's to redline. At .9bar you should have enough fuel delivery unless you have a cam, ports, and or are running big boost.

There are things that can be done on the ignition side but mostly make sure your total advance under boost is about 24-25 deg.

This is the basics.

[djdawson2]

[quote=911st;4713228]What year. What exaust.

It is an '89, and the exhaust appears to be stock.

I look at the 7200 turbo option with some skepticism. My Audi experience with KKK turbos includes using the K24 7200, which is the same compressor section and a smaller hot side. This turbo, on a 2.2 running 28psi (1.9bar) will make about 325whp max, and it runs out of gas around 6k rpm. I find myself wondering how the same compressor will supply an engine of 50% greater capacity, while delivering air in an efficient part of the map.

Pure speculation, since you can't see a compressor map... but my guess is that the 7200 can only deliver about 35 lbs/min efficiently... whereas a GT30R Garrett can deliver about 50 lbs/min. Even a GT35 looks to me to be way larger than required for the 930, given apparent limitation on the boost levels one can run.

I've got to say that some experimentation is tempting to me, as I have both a GT3071 and a 3076 (30R) sitting idle in my garage. It would only cost me same minor fabrication to give them a try, as their mounting dimensions are identical.

The IC... is the stock one *that* bad? What are the best options, given the requirement to retain my A/C?

Again, thanks for the input.

Dave

[krasuskyp]

*oh snap*!



bwhahahahaa... ... Love it.

[911boost]

Since you are talking 1/4 mile times, you may want to save some $$ for a new clutch.

[RarlyL8]

The 7200 will not fulfill the requirements you list. Pulling hard through redline is what the K27HF is designed to do, the 7200 falls off after ~5500 or so.
The most broad range on-boost from a K27 series turbo comes from the HFS. To take full advantage of the capabilities requires larger tubing for the cold side inlet.
If you have a GT30R right now then it is just a matter of fabrication to install it.
Ben (M&K) had a GT30R on his engine and now has a K27-7200. Slightly different application (Carrera engine) but may have some insight into the differences.

[djdawson2]

Originally Posted by krasuskyp

*oh snap*!

bwhahahahaa... ... Love it.

Hey, it was only a matter of time...

[jwasbury]

I've got Brian's (RarlyL8) SSI set up, and stock-exit muffler along with a UMW K27S, which is a modified 7200 I guess. I run the factory boost level and will continue to do so until I get an upgraded I/C (or perhaps never because I plan to raise static compression ratio when I rebuild the engine).

I'm pretty happy with this set up. Boost comes in quickly and the car pulls hard. Maybe not the best choice of parts for maximum HP, but it works for me on the street. Keep in mind that my '79 had the restrictive US specific exhaust system that is universally known as a POS. Your $ may be better spent on something besides new heat exchangers.

I keep reading about the 7200 turbo running out of juice at high rpm and must say that its not something that I have noticed. Perhaps ignorance is bliss. I know in my car that once the boost is on, redline comes very quickly. In 1st gear almost too quick. After second gear if you're still running to redline, you're well into go directly to jail speeds. Perhaps on a dyno chart, the 7200 fails to produce a curve that earns bragging rights, but for me, in the real world on the street I can't complain.

Paul and I will be convoying to Turbopalooza later this month, so he can perhaps provide you with some real-world experiences with my set up.

[djdawson2]

[quote=RarlyL8;4714034]The 7200 will not fulfill the requirements you list.

Yep, I kinda figured that based on my experience with K24 7200 turbos. Just not enough flow.

Pulling hard through redline is what the K27HF is designed to do, the 7200 falls off after ~5500 or so.

Are there compressor maps to support the performance of the "HF?"

The most broad range on-boost from a K27 series turbo comes from the HFS. To take full advantage of the capabilities requires larger tubing for the cold side inlet.

I figure I'll be doing that anyway to try various options.

If you have a GT30R right now then it is just a matter of fabrication to install it.

Had assumed same... since the K27 hot side inlet has the same dimensions as a T3 inlet. Should only be oil lines and accumulator mods. I have several GT series turbos "sitting around" that I could try. I would just need to get a more appropriate hot side (1.06) for them.

Ben (M&K) had a GT30R on his engine and now has a K27-7200. Slightly different application (Carrera engine) but may have some insight into the differences.

I'd sure like to hear about that one. It's time to do some math... guessing on the VE of the 930 engine. The GT30 moves enough air to do the job. Sounds like an adjustable (or programmable) WUR will be required to insure fuel delivery.

What hot side is typically used on the KKK 7200? #8?

Thanks,

Dave

[djdawson2]

Originally Posted by jwasbury

Paul and I will be convoying to Turbopalooza later this month, so he can perhaps provide you with some real-world experiences with my set up.

Thanks for the feedback. Does anyone on here ever validate their seat of the pants impressions... like with a g-tech?

Dave

[911st]

Your altitude might require a larger turbo by its self.

In my 3.3 car with big ports, SC cams, headers, and C2T intercooler that was modified with a larger core I did a lot of tuning on the dyno with a K27-7200.

I could not pull 1 bar to red line but could hold about .9 bar +/- using my EBC. On my car with a 7200 the limit was about 330 rwhp (heavy 17" RUF rims) or about 385fwhp. I stayed with this turbo over big ones as I loved how soon and hard boost came it. On top of that even with a change to euro fuel head, lines, injector and what was basically an Andial fueler, I was at my fuel limit anyway so a biger turbo would take me to a lean part of the RPM range where I really did not want to spend much time.

If you were at sea level and going to stay under .9 bar and limit your mods, the K27-7200 might be a great turbo.

My other turbos were a K29 and an early HF with a little larger hot side (7006 based). The big turbos did start to boost a bit before the 7200. However, they did not reach full boost untill about 3600-3700. My K27-7200 started to boost a little later but reached full boost near 3k to 3.1k.

The K29 & HF did pull a little bit better to red line but I chose the kick of the K27-7200.

As the HF had an even larger compressor wheel than my K29, I did experance some issues with overboost. Even though mine was based on the 7006 that had a larger hot side than the current quick spools. I could not hold boost down to .8 bar. With the help of an EBC, Tial w .7 bar spring and a boost setting of 1 bar I could keep overboost mostly at bay.

I wonder if a lot of the excitment of the HF's and such could be do to the extra HP that comes with overboost. There was a lot of discussion about overboost of the developer of the HF when it first came out but that seems to have gone to the way side.

I have heard good things about the GT turbos but have no experance with them.

If the K27-7200 is a sunk cost, try it you might like it. However, put the lowest restriction muffler with it you can live with for the best power and boost response.

In my day the best muffler was a Borla straight through muffler we made up ourselves with an exit on the passangers side.

As to running big boost, going from .8 bar to .9 bar is about 15hp. Then steping up to 1 bar is about another 15hp.

One of the monster builds here only gets about 25hp going from .8 to 1 bar. However, everything is optimized so he makes 500rwhp at .8 bar. You do not need big boost to make HP.

[iamchappy]

Or go with short gears in your tranny, this may limit your top end to under 140 but man you will get there fast.

[krasuskyp]

Originally Posted by djdawson2

Thanks for the feedback. Does anyone on here ever validate their seat of the pants impressions... like with a g-tech?

Dave

I'll bring my RaceTechnology AC-22 along with me and we'll compare mine to Jacob's - will least give you an ideaski. And my bud up the road runs a K29 in his twinplug'd Kokeln'd '79, I'll give it a whirl in that too for shiggles.

[Garrison]

I too am starting down the path, and am wondering what the "mile high" altitude will do to the car. I will say that the 930 does seem slow compared to what I expected, but then again my car is 26 years old...

I will be watching to see what you come up with. I am still trying to figure out the best turbo for the thinner air, and the performance that I want...

[djdawson2]

Originally Posted by Garrison

I too am starting down the path, and am wondering what the "mile high" altitude will do to the car. I will say that the 930 does seem slow compared to what I expected, but then again my car is 26 years old...

I will be watching to see what you come up with. I am still trying to figure out the best turbo for the thinner air, and the performance that I want...

Cool... a local to me. I'll keep my activities posted on this forum. Feel free to contact me privately if you ever want to chat about stuff you're doing. Also, I have a well equipped garage if you ever need help doing something with your car... lift, tire machine and balancer, tig welder, etc... but keep in mind that I do live on a dirt road.... = dusty car.

Dave

[WinRice]

I'm in Castle Rock and run the K27HFS, specifically for the altitude.

The thing you need to be concerned with is pressure ratio and mass flow.

For example (rounding off for simplicity), if your goal is to run 2 bar absolute pressure at the manifold:

Sea Level
Atmospheric Pressure = 1 bar (roughly)
Boost = 1 bar above atmospheric
Absolute manifold Pressure = 2 bar
Pressure Ratio = 2.0

6000 ft
Atmospheric Pressure - 0.8 bar (roughly)
Boost - 1.2 bar above atmospheric
Absolute manifold Pressure = 2 bar
Pressure Ratio = 2.5

An increase from a 2.0 to a 2.5 pressure ratio is a pretty big increase for some turbos to handle well, depending on the compressor design and map.

Whatever you choose needs to be able to sustain the mass flow at the pressure ratio you choose. That's aways been the problem with Pikes Peak hill climb cars is being able to size the turbo to work well from start to finish, trying to compensate for the altitude change.

You also need to know whatever gauge you are using to measure boost, is referenced to sea level, or to the current atmospheric pressure, so you know where to set the boost. In the above example, a gauge referenced to sea level would read 1 bar, a gauge referenced to the current atmospheric pressure would read 1.2 bar. Error the wrong way could have bad consequences.

FWIW I run my K27HFS at 1.2 bar on a gauge referenced to my current altitude, and it will hold that boost to redline. I also use an HKS EBC so I can back the boost down if I go to lower altitudes.

BTW I keep my redline at 6400, because of stock rod bolts (for now), and also for the CIS. It's about the max the CIS will flow at that boost level.

[djdawson2]

[quote=WinRice;4716335]

An increase from a 2.0 to a 2.5 pressure ratio is a pretty big increase for some turbos to handle well, depending on the compressor design and map.

Yep... take a look at the map for the GT30R when you get a moment. It is a very happy camper delivering air at PRs in the mid to upper 2's, while efficiently moving 50+ lbs/min of air... plenty for any CIS based hp goals.

Unfortunately, I can not draw any conclusions with the KKK offerings because there are no publicly available maps.

Dave

[WinRice]

Originally Posted by djdawson2

Unfortunately, I can not draw any conclusions with the KKK offerings because there are no publicly available maps.

Dave

Yep, my problem exactly. I wish I had compressor maps to compare to, but I spoke with Stephen and Kevin and was assured it would flow enough. So I took a gamble on it. So far it's worked out, and I've been running it for 4 years now.

When I get a breather I'll look at the GT30R. Your biggest problem is going to be fueling with CIS. The stock system is limited, 400 RWHP to 450 RWHP with mods.