Old School Technology for an Old School Car.
07-05-2004, 12:08 PM
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Old School Technology for an Old School Car.
Here is the Rebuilt K29/K27 Audisport turbo from their 1985 Pikes Peak Attempt. The Turbo on the Left is an RS2 7200 Comp for comparison. Majestic Turbo in Waco did the Rebuild and I had them improve the performance of this old turbo as much as possible. A tapered nosecone was added that is so shiney its hard to photograph. This should help maintain laminar flow into the turbo. The Coldside housing is marked 5329 101 5091 and is 3 of 15 in this batch. According to KKK this was a special run of 15 turbos made for Audi for use in 1985. I have two and three. The backplate is marked 5328 151 5792 which means its from a K28 turbo. The Center and hotside are 100% K27.
<img src="http://www.bufkinengineering.com/Rebuiltk27-1.JPG">
The two Hotsides for Comparison. The RS2 is using a #6 K26 hotside. Which corresponds to a 0.6 A/R. The Audisport hybrid is using a K29 #9 hotside. Notice the round hole on the K27 hotside which makes it particular to Audi K27 Manifolds. Porsche K27 turbos have a rectangular Flange on their K27s. The Audi Sport Quattro used a #7 K27 turbocharger and would develop full boost by 4000 rpm.. According to Lehmann this turbo should spool about 500rpm later than a #7 housing. I have a Sport Quattro turbo on order and it should be here in a few weeks. Expect a 2nd side by side comparison then.
<img src="http://www.bufkinengineering.com/Rebuiltk27-2.JPG">
Majestic's machining work to reduce the weight of the K27 wheel. K27 wheels are much heavier than their K26 counterparts, especially on the nut in the hotside. This nut has been machined away and hollowed out. Notice on the RS2 that the nut has been completely ground away for a slight reduction of weight. There is a stamping on the hotside flange which has a date on it. 6.8.85 (June 8, 1985) A test run date for the 1985 Pike's Peak Event. Turbine outlet diameter is 66mm
<img src="http://www.bufkinengineering.com/Rebuiltk27-3.JPG">
<img src="http://www.bufkinengineering.com/Rebuiltk27-4.JPG">
A picture of the nosecone. Notice the 3 of 15 mark. Inlet Diameter is 62mm.
<img src="http://www.bufkinengineering.com/Rebuiltk27-5.JPG">
The #9 stamping on the inside of the hotside. According to Lehmann the majority of Audisport race vehicles (S1s, TransAm, Imsa) were fitted with at least a #9 hotside. A larger hotside was used on many occasions. Use of a turbo this large requires prodigious use of left foot braking to maintain boost pressure, but when done right the results are fantastic.
<img src="http://www.bufkinengineering.com/Rebuiltk27-6.JPG">
edit: I came this close (fingers really close together) to ordering a GT35R, but in the end, I'm going to keep my car as original as possible. If this turbo doesn't work out, I have the Sport Quattro spec K27 which I can use.
<img src="http://www.bufkinengineering.com/Rebuiltk27-1.JPG">
The two Hotsides for Comparison. The RS2 is using a #6 K26 hotside. Which corresponds to a 0.6 A/R. The Audisport hybrid is using a K29 #9 hotside. Notice the round hole on the K27 hotside which makes it particular to Audi K27 Manifolds. Porsche K27 turbos have a rectangular Flange on their K27s. The Audi Sport Quattro used a #7 K27 turbocharger and would develop full boost by 4000 rpm.. According to Lehmann this turbo should spool about 500rpm later than a #7 housing. I have a Sport Quattro turbo on order and it should be here in a few weeks. Expect a 2nd side by side comparison then.
<img src="http://www.bufkinengineering.com/Rebuiltk27-2.JPG">
Majestic's machining work to reduce the weight of the K27 wheel. K27 wheels are much heavier than their K26 counterparts, especially on the nut in the hotside. This nut has been machined away and hollowed out. Notice on the RS2 that the nut has been completely ground away for a slight reduction of weight. There is a stamping on the hotside flange which has a date on it. 6.8.85 (June 8, 1985) A test run date for the 1985 Pike's Peak Event. Turbine outlet diameter is 66mm
<img src="http://www.bufkinengineering.com/Rebuiltk27-3.JPG">
<img src="http://www.bufkinengineering.com/Rebuiltk27-4.JPG">
A picture of the nosecone. Notice the 3 of 15 mark. Inlet Diameter is 62mm.
<img src="http://www.bufkinengineering.com/Rebuiltk27-5.JPG">
The #9 stamping on the inside of the hotside. According to Lehmann the majority of Audisport race vehicles (S1s, TransAm, Imsa) were fitted with at least a #9 hotside. A larger hotside was used on many occasions. Use of a turbo this large requires prodigious use of left foot braking to maintain boost pressure, but when done right the results are fantastic.
<img src="http://www.bufkinengineering.com/Rebuiltk27-6.JPG">
edit: I came this close (fingers really close together) to ordering a GT35R, but in the end, I'm going to keep my car as original as possible. If this turbo doesn't work out, I have the Sport Quattro spec K27 which I can use.
07-06-2004, 05:00 AM
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Got me wondering
Turbo is new to me, I'm old school with the 90 NA motor. But mine supposedly has an RS2 unit in it, along with a stock turbo as a spare. You can see a huge difference between the stock and "installed" turbo, but I though I was told it was a K28 not a K27. In any event it at least looks bigger than the one in your picture. I can measure the inlet size easily, I have the 34mm restrictor that I can use to check the inlet diameter. It's buried fairly well, but I'll try and check the casting's to see what they tell me too.
07-06-2004, 08:55 AM
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Re: Got me wondering
In regards to your car,
RS2 makes alot of sense for a rally car that has to run an intake restrictor. If the car can't breath anyways from the restrictor, why put a huge turbo on there with alot of lag. So.. I'd be surprised to see a K27 or K28 turbo on a car with an intake restrictor. The K27 turbine shaft is much heavier than a K26 or RS2 shaft which means you would have the worst of both worlds. Lag and no-top end power. If your car has the restrictor fitted, then a smaller turbo like a K26 makes more sense. For a dedicated race car that will run over 4000 rpm all the time, an RS2 is smallish and will be a big heat pump at high boost. There are more logical choices to make for that application, but maybe not so if a restrictor is part of the equation.
Lehmann made something called a Group A(IIRC) turbocharger which many of the people in the US adopted cause of the intake restrictor rule. From its description, its gotta be similar to an RS2 since its based on a high performing K26 unit. But it was fitted with a 40mm restrictor which ultimately limited top-end power and added more low-end torque.
A K28 is a huge turbo. K27 is very big as well, seeing as how that was stock on only one Audi, the Sport Quattro. I'd only envision something larger than a K27 in an unrestricted series like what Audi ran in the 80s (IMSA, Trans Am, Group B)
RS2 makes alot of sense for a rally car that has to run an intake restrictor. If the car can't breath anyways from the restrictor, why put a huge turbo on there with alot of lag. So.. I'd be surprised to see a K27 or K28 turbo on a car with an intake restrictor. The K27 turbine shaft is much heavier than a K26 or RS2 shaft which means you would have the worst of both worlds. Lag and no-top end power. If your car has the restrictor fitted, then a smaller turbo like a K26 makes more sense. For a dedicated race car that will run over 4000 rpm all the time, an RS2 is smallish and will be a big heat pump at high boost. There are more logical choices to make for that application, but maybe not so if a restrictor is part of the equation.
Lehmann made something called a Group A(IIRC) turbocharger which many of the people in the US adopted cause of the intake restrictor rule. From its description, its gotta be similar to an RS2 since its based on a high performing K26 unit. But it was fitted with a 40mm restrictor which ultimately limited top-end power and added more low-end torque.
A K28 is a huge turbo. K27 is very big as well, seeing as how that was stock on only one Audi, the Sport Quattro. I'd only envision something larger than a K27 in an unrestricted series like what Audi ran in the 80s (IMSA, Trans Am, Group B)
07-06-2004, 03:25 PM
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It's got lag
It was built by Buffum to copy his S2 that Paul was running. The Lehmann ECU indeed was intended to have the 40mm restrictor in place. BUT, since it was built it was tinkered with, and the guy I bought it from put in the "big" turbo. Unfortunately he has little technical background, so asking him a bunch of questions is pointless. He changed the turbo, and switched gearboxes too. It used to have the 4.86 gears, and with the smaller turbo, probably had much less lag. Now, with the big turbo, and 4.11 gears, it's not where it should be.
It's got enough power up to around 4k, but then it really comes on, and it's a bit scary. In first through third the tyres just break free, and you get that time warp feeling, as everything flies by. With the 90 20V NA, it's there right from the get-go, so there are no surprises. It launches off the line without any lag, and pulls right up to 8k.
I plan on at least going back to the other gearbox, and am still up in the air about the turbo. I've got the spares, so I can go either way, just not sure what I want it to do just yet.
I pulled the spare turbo out of the box, and it's a K24, nothing special. Tomorrow I'll try and look at the other one, and see what it is.
It's got enough power up to around 4k, but then it really comes on, and it's a bit scary. In first through third the tyres just break free, and you get that time warp feeling, as everything flies by. With the 90 20V NA, it's there right from the get-go, so there are no surprises. It launches off the line without any lag, and pulls right up to 8k.
I plan on at least going back to the other gearbox, and am still up in the air about the turbo. I've got the spares, so I can go either way, just not sure what I want it to do just yet.
I pulled the spare turbo out of the box, and it's a K24, nothing special. Tomorrow I'll try and look at the other one, and see what it is.
07-07-2004, 07:21 AM
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The only two I have so far
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07-08-2004, 06:49 PM
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wonderful post!
great to see you keep your car true to its roots. Not having the wealth of spares that you do, I did cave a bit and go with a hybrid Garrett/KKK replacement. Wouldn't it be interesting to see how the cars would perform side by side at a racetrack? 
07-08-2004, 06:52 PM
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squidix9, have we met before?
I could swear that I have seen your car at Rudy's shop? I like to drop in and pick his brain periodically, and the first thing that caught my eye were the wheels on your car! First the offset, then the bolt patern..
07-09-2004, 04:48 AM
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Yes and no
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The car was up in Rudy's shop for quite awhile. I just bought it last week, and took it out.
The wheel's are the original Fuch's from the SportQ. They do have a wicked offset, giving it a nice profile front/rear. Unfortunately the left front is a bit out of round.
The pattern is 5X112 as opposed to 4X108. The Coupe (My Coupe) has the GroupB steel struts. James' A1 and my 90 have the alloy S1 struts. mine being the EVO-II style with the new lower spring perches. I haven't looked that closely at James' to see which ones his are.
The car was up in Rudy's shop for quite awhile. I just bought it last week, and took it out.
The wheel's are the original Fuch's from the SportQ. They do have a wicked offset, giving it a nice profile front/rear. Unfortunately the left front is a bit out of round.
The pattern is 5X112 as opposed to 4X108. The Coupe (My Coupe) has the GroupB steel struts. James' A1 and my 90 have the alloy S1 struts. mine being the EVO-II style with the new lower spring perches. I haven't looked that closely at James' to see which ones his are.