Gt30 or s206
31 October 2012, 12:31 AM
#31
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We've built several using the 35 billets, and believe me, you'd be amazed at how flexible they are considering we're talking 500 bhp and beyond.
31 October 2012, 12:50 AM
#32
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If you look at Martyn's graph, you'll see that was logged three years ago!
As you appear to be interested, Mike's developed a slight misfire at idle which we investigated. It turned out that the stock seat in one head had shifted due to cracking from the plug thread (a common problem) so we've cut out the offending seat area, rewelded, and now we're rebuilding it.
This is how it all looks
Head cracking; We've seen plenty like this, one or two with a compromised seat. (This is a head we took a picture of some time ago and is for demo purposes only.)
We prepare them by cutting out the seats and welding the affected area
This is the same head (Mike's) after counterboring and restoring the seats and plug threads, ready for final fettle
The finished result will look similar to this;
We're taking the opportunity to carry out more port and throat work while we're at it.
Of course, it takes engineering to be able to carry out this sort of work, not merely spanners or box shifting.
Please note that we are talking about Subaru cylinder head problems here, and this sort of issue will be applicable to any engine, not only 2.1's (stating the bleeding obvious I know)
If you'd like to know anything else, just ask!
As you appear to be interested, Mike's developed a slight misfire at idle which we investigated. It turned out that the stock seat in one head had shifted due to cracking from the plug thread (a common problem) so we've cut out the offending seat area, rewelded, and now we're rebuilding it.
This is how it all looks
Head cracking; We've seen plenty like this, one or two with a compromised seat. (This is a head we took a picture of some time ago and is for demo purposes only.)
We prepare them by cutting out the seats and welding the affected area
This is the same head (Mike's) after counterboring and restoring the seats and plug threads, ready for final fettle
The finished result will look similar to this;
We're taking the opportunity to carry out more port and throat work while we're at it.
Of course, it takes engineering to be able to carry out this sort of work, not merely spanners or box shifting.
Please note that we are talking about Subaru cylinder head problems here, and this sort of issue will be applicable to any engine, not only 2.1's (stating the bleeding obvious I know)
If you'd like to know anything else, just ask!
31 October 2012, 11:35 AM
#35
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As far as the engine is concerned, it isn't a turbo issue, it's only about cylinder fill being adequate for the purpose of power production.
It helps to bear in mind what's happening. As far as the engine is concerned, the actual output is of no consequence, assuming that the infrastructure can stick what you're asking of it.
What makes an engine "go pop"?
Usually, it's some secondary cause, such as inadequate or incorrect fuelling, poor or over ambitious ignition or boost control, or any one of a dozen reasons linked to bad design or poor maintenance. I'd say missing a gear is pretty much up there as well, along with other driver induced maladies.
A well put together Impreza engine with nice clean internals will put up with a lot, considering the fact that they aren't a precision instrument, from a purely engineering viewpoint. We have to carry out corrective machining all the time, just to fix factory issues.
We built one 2.1 going back several years ago that suffered from "Mission Creep". This is where we build an engine of a particular spec, that then ends up being pushed well beyond that target. We only used basic forged rods and pistons, but it ended up running well over 600 bhp, and carried on doing that, despite severe provocation on road and track until only recently. Eventually, it decided it didn't want to be doing that any more, but that wasn't a fault of the motor itself, and only after it actually ended up giving well over 700 bhp!
That particular car now runs another of our 2.1's.
There is no reason why 550 bhp should be more of an issue than 500, assuming you have everything you need to operate at that level in terms of quality of component and specification. The big difficulty comes in when you're asked to provide a finished product that has vital parts missing on grounds of cost.
Given the option, I'd always want to "turn the wick down" from what is actually possible to a level where it's slightly more forgiving, considering what some people do with them! It's like climbing Everest. Sooner or later, you end up in the "Death Zone"
We built the engine for Paul Doyle's Time Attack car. He's used it for a good number of meetings since, running at around 800 bhp using a Nitrous shot.
The car is well put together, and he has a great team back up. As far as I'm concerned, as an engine builder, that's as far as we're likely to go in terms of proving that we can cut it. If a race engine lasts for one race, that's as much as anybody can expect, although Paul hasn't been off the podium since it went in.
As to your 500/550 question, you can either go for a more relaxed output from the GT35 (more top end for less boost) or run the S206 up with a touch of methanol and a bit more boost. Your choice!
31 October 2012, 11:43 AM
#38
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35 is an amazing turbo but unless it's a drag specific car is complete over kill IMO. 30 with a .63 is a much better option, especially on a 2.1
31 October 2012, 11:45 AM
#39
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Mike's car runs a GT30 billet, we like that one too!
Horses for courses..
Horses for courses..
31 October 2012, 12:04 PM
#41
although its costing me a fortune 
as you guys well no that.But to get the same feeling on a production car would cost 10 times as much and even then I'm not sure it would be as good. after all of your comments I feel is got to be a billet 30 so now what the difference between the housings .63 and I think its a .83 
31 October 2012, 12:09 PM
#42
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It will spool earlier on a .63 housing but make a little more top end on a .82
A .82 will make it slightly more laggy tho and IMO Thr whole point of a 30 is the benefits of improved spool
You'd have to have some car and be some driver to max out a 30 on track to the point where you needed to upgrade turbo's.
John Stevenson is a seriously good pilot and the 30 is good enough for him.
A .82 will make it slightly more laggy tho and IMO Thr whole point of a 30 is the benefits of improved spool
You'd have to have some car and be some driver to max out a 30 on track to the point where you needed to upgrade turbo's.
John Stevenson is a seriously good pilot and the 30 is good enough for him.
Last edited by need4speeduk; 31 October 2012 at 12:14 PM.
31 October 2012, 12:11 PM
#44
I think I'm a bit old to wave my ***** especially in puplic but for me it's driving a stripped out type r with big hp on track of course although its costing me a fortune as you guys well no that.But to get the same feeling on a production car would cost 10 times as much and even then I'm not sure it would be as good. after all of your comments I feel is got to be a billet 30 so now what the difference between the housings .63 and I think its a .83
although its costing me a fortune as you guys well no that.But to get the same feeling on a production car would cost 10 times as much and even then I'm not sure it would be as good. after all of your comments I feel is got to be a billet 30 so now what the difference between the housings .63 and I think its a .83
31 October 2012, 12:17 PM
#46
31 October 2012, 12:18 PM
#47
This is a huge learning curve for me and I thank you all for not only your opinions but for you to share your experiences I want to use my car for track racing sprints maybe time attack but I think I should learn to walk first the gt30.63 billet looks to be my best option
31 October 2012, 12:20 PM
#48
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One of the 2.1 strokers we're running in at the moment is going to Gibraltar when it's finished. It's a track day car.
With the extra heat out there and it's intended use, being able to run a GT35 at .2 bar less than a GT30 to achieve the same power is very desirable.
The fact that it takes a little longer to get there is barely worth mentioning.
31 October 2012, 12:27 PM
#51
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31 October 2012, 01:04 PM
#53
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That's the problem of course, it's all a matter of opinion which is owner specific.
One of the 2.1 strokers we're running in at the moment is going to Gibraltar when it's finished. It's a track day car.
With the extra heat out there and it's intended use, being able to run a GT35 at .2 bar less than a GT30 to achieve the same power is very desirable.
The fact that it takes a little longer to get there is barely worth mentioning.
One of the 2.1 strokers we're running in at the moment is going to Gibraltar when it's finished. It's a track day car.
With the extra heat out there and it's intended use, being able to run a GT35 at .2 bar less than a GT30 to achieve the same power is very desirable.
The fact that it takes a little longer to get there is barely worth mentioning.
I had charge temp issues when running the 35 but none since swapping to a 30.
As you said, each to their own. Personally I think a 35 on a 2.1 isn't the most compatible or optimum combination.
31 October 2012, 01:06 PM
#54
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There seems to be a ready market for used turbos, so I don't suppose it matters. We're swopping them around all the time, on occasion having several cars lined up while we play "pass the turbo"
31 October 2012, 01:11 PM
#55
Surely with the added heat out there a 30 would be a better choice as the heat generated from the bigger turbo would surely exceed the .2 bar less you mentioned.
I had charge temp issues when running the 35 but none since swapping to a 30.
As you said, each to their own. Personally I think a 35 on a 2.1 isn't the most compatible or optimum combination.
I had charge temp issues when running the 35 but none since swapping to a 30.
As you said, each to their own. Personally I think a 35 on a 2.1 isn't the most compatible or optimum combination.
31 October 2012, 01:13 PM
#56
Surely with the added heat out there a 30 would be a better choice as the heat generated from the bigger turbo would surely exceed the .2 bar less you mentioned.
I had charge temp issues when running the 35 but none since swapping to a 30.
As you said, each to their own. Personally I think a 35 on a 2.1 isn't the most compatible or optimum combination.
I had charge temp issues when running the 35 but none since swapping to a 30.
As you said, each to their own. Personally I think a 35 on a 2.1 isn't the most compatible or optimum combination.
but agree a billet 30 on a 2.1 would be my preferred combination
31 October 2012, 01:25 PM
#57
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Both are extremely good turbo's. Maybe I prefer the 30 cos I couldn't handle the car with a 35 on lol
Nice repair job on those heads btw
31 October 2012, 01:54 PM
#59
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Thanks, done a few now. Costly process, but nothing like as costly as buying new heads especially when they have already been worked.
31 October 2012, 02:00 PM
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