As I now have one of these beauties, I decided to do some research.
Compressor wheel inducer bore is 48mm. This smalll little baby becomes extremely inefficient at anything more than 27/28lbs of air/hr.
The compressor wheel is similar to a T3-60 wheel. Smaller than a T04E-46. It's probably happy at 11/12psi on a stock system.
This is the reason that these cars make a nice tq number and no HP when running elevated boost levels.
Looks like the largest k27 wheel available is 52.5mm.
Just a FYI.
http://www.melett.com/pdfs/KKK/3K%20K27.pdf
Todd
745i-k27 turbo info
Todd, this is the k27 Porsche turbo set-up I have been looking at. Thought it might be possible to use the cold side with the factory hot side so it would mount to the factory manifold.
Vance
Vance
My turbo guy can upgrade the wheel to the 52mm wheel but I do not know if it's really worth the time and expense.vance wrote:Todd, this is the k27 Porsche turbo set-up I have been looking at. Thought it might be possible to use the cold side with the factory hot side so it would mount to the factory manifold.
Vance
Todd
Me too.............. Thanks Todd 
Vance maybe we should have the spare Turbo Modded and swap it out one at a time. Me first 
Last edited by johnnye23 on Mar 20, 2007 10:39 AM, edited 1 time in total.
Can you also post how much your turbo rebuilder charges to "go through" a k27? I don't know if this normally includes a new CHRA or not, but I would be interested to know. I would also be interested in your opinion of this rebuilder's work (i.e. highly recommended, or just the guy who is closest to you) - I have a rebuilder out here in Cali. too, but don't know if they know the "in's-and-out's" of these beasts.T_C_D wrote:I'll post a price as soon as it is available. I have a k27 arrving at the turbo shop first of next week. They have a 60 trim wheel and are going to look at it right away.
Todd
Best,
Mark
I have been using this shop for 7 years. They have never failed me and are fairly priced. Figure $400 for a basic k27 rebuild.wickahead wrote: Can you also post how much your turbo rebuilder charges to "go through" a k27? I don't know if this normally includes a new CHRA or not, but I would be interested to know. I would also be interested in your opinion of this rebuilder's work (i.e. highly recommended, or just the guy who is closest to you) - I have a rebuilder out here in Cali. too, but don't know if they know the "in's-and-out's" of these beasts.
Best,
Mark
Todd
I can say through experience that not only does the compressor suck compared to newer turbos in respect to spooling up -- for a small thing it should spool up hellishly fast... it doesn't.
Also, around 5000rpms it stops making power - the thrust starts to fall and there isn't anything you can do about it.
Also, around 5000rpms it stops making power - the thrust starts to fall and there isn't anything you can do about it.
I hear ya.Tjn182 wrote:I can say through experience that not only does the compressor suck compared to newer turbos in respect to spooling up -- for a small thing it should spool up hellishly fast... it doesn't.
Also, around 5000rpms it stops making power - the thrust starts to fall and there isn't anything you can do about it.
For my purposes, the 745 kit will work fine for now, because I already have a (free to me) 745, a 524td to shove it into (an '85 w/o ABS so the intercooler will fit), and it will be a good first step.
Eventually, I will put a nice TCD kit in my other 524td.
...one project at a time
Not to throw in a monkey wrench but I have been talking to these guys(http://imagineauto.com/Merchant2/mercha ... =930turbos) for a while and from the sound of it their K27 will work on our 745i.
I am not sure what the differences are compare with Todd's mod but I bet we can steal some of their mods for our use to help with spooling and sustaining.
Anyone here from Lenexa, KS?
I am not sure what the differences are compare with Todd's mod but I bet we can steal some of their mods for our use to help with spooling and sustaining.
Anyone here from Lenexa, KS?
Doesn't the stock 535i start to choke up at about 5k rpm? The b34 isn't really a top end screamer, judging by the dyno charts I've seen. As long as the stock 745 turbo can maintain whatever boost pressure youre using without heating up the charged air, theres no reason for the power to drop off unless VE starts to. If a turbo can make, say, 8 psi from 2k until 6k, and is 70% efficient, the powerband will be very much like the stock curve, just much stronger. You can't force air into a motor despite crappy cam timing. I think the best upgrade would be a b35 cam, as opposed to a larger turbo. It'd probably be cheaper, and almost certainly more effective.Tjn182 wrote:I can say through experience that not only does the compressor suck compared to newer turbos in respect to spooling up -- for a small thing it should spool up hellishly fast... it doesn't.
Also, around 5000rpms it stops making power - the thrust starts to fall and there isn't anything you can do about it.
Todd,
While your half correct, the b34 will not make more power in stock form past 5.1k. Even boosted, the best you can get is a flat power curve past 5k. Ive not seen a stock b34 power curve rise past 5k in any dyno.
So "choking" is kinda correct.
RussC
While your half correct, the b34 will not make more power in stock form past 5.1k. Even boosted, the best you can get is a flat power curve past 5k. Ive not seen a stock b34 power curve rise past 5k in any dyno.
So "choking" is kinda correct.
RussC
T_C_D wrote:No. Not boosted.turbodan wrote: Doesn't the stock 535i start to choke up at about 5k rpm?
You forgot about my first 3.2L 745i that made peak HP at 6500rpm.russc wrote:Todd,
While your half correct, the b34 will not make more power in stock form past 5.1k. Even boosted, the best you can get is a flat power curve past 5k. Ive not seen a stock b34 power curve rise past 5k in any dyno.
So "choking" is kinda correct.
RussC
That was not a "stock" b34.
RussC
RussC
T_C_D wrote:You forgot about my first 3.2L 745i that made peak HP at 6500rpm.russc wrote:Todd,
While your half correct, the b34 will not make more power in stock form past 5.1k. Even boosted, the best you can get is a flat power curve past 5k. Ive not seen a stock b34 power curve rise past 5k in any dyno.
So "choking" is kinda correct.
RussC
-
Velocewest
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So what's the bottleneck there? The stock flow through the head? The AFM? ( I think it's funny the AFM necks down to significantly smaller that any of the rest of the intake system at the entrance where it gets rectangular...)russc wrote:Todd,
While your half correct, the b34 will not make more power in stock form past 5.1k. Even boosted, the best you can get is a flat power curve past 5k. Ive not seen a stock b34 power curve rise past 5k in any dyno.
So "choking" is kinda correct.
Even 2v heads can be made to run top end. I've seen some dynos with hot cams and ITB's that made remarkable power remarkably high up. The one thing I've never seen from a tuned BMW 2v engine is a good low end. 4v engines like the s54 or s38 always seem to have more low end and a less remarkable climb onto the powerband. A very flat torque curve. The most aggressive 2v motors always take a big step onto the powerband. I prefer that kind of engine. I also grew up racing two strokes. Coincidence?T_C_D wrote:The 2 valve cyl head.c_spargo wrote:
So what's the bottleneck there? The stock flow through the head? The AFM? ( I think it's funny the AFM necks down to significantly smaller that any of the rest of the intake system at the entrance where it gets rectangular...)