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Underbody braces, turbos and more!

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PostPosted: Tue Dec 03, 2013 12:10 am 
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Hello all, I have been a lurker here for quite sometime and have been fascinated by these engines for about as long. A little back story about myself. I have been designing and developing race engines for quite some time and I am about to embark on a project which hopefully will make all T3 people proud.

This engine is to be built for the SCCA SR1 class which will begin next year. There current rules allow turbocharging of upto 670ccs. They have imposed a inlet restrictor of 32mm but this is for 4valve bike engines. I have gotten the go ahead to build a 2v automotive based engine unrestricted of the same displacement. I use the software "Engine Analyzer Pro" and have modeled from specs I found here a de stroked Mk2 T3.
Image
This is the modeled dyno graph.

The engine is quite neat and I am asking for some input and possibly a few pictures if they are available.

The heart of the engine is a destroked crank. 2" stroke to be exact. This coupled with a miata length(133mm) and Vitara piston will yield an acceptable deck height for a stock block. The stock head I am planning to revamp with not radical but lets say "generous" port work mostly involving a bridgeport and a tig. It still uses 33mm/30mm valves intake and exhaust respectively. I have spent many hours on cam design and have one that works very well for the given setup as shown by the power graph. Intake manifold and turbo headers will of course be fit to the application but lenghts and runner volume have all been tested.

I have a couple questions.
1:has anyone developed a race engine of this type to this extent here?
2:Has anyone sawed a head to get an idea on true port shape and what is in the way to stop radical port reshaping? The exhaust ports appear to have water flow over them? can/has anything drastic been done to avoid this? ie cut out and weld plates over the water jackets?

Cheers and I will keep updating as progress ensues. I am getting a core engine to start the development work and hopefully have a running engine by spring for the upcoming season.

Any thoughts are welcome..


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PostPosted: Tue Dec 03, 2013 12:20 am 
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That's roughly 50% more than the output we're seeing with some well prepared ones. Tell us exactly how you're going to do that, and let us in on this cam design while you're at it.

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PostPosted: Tue Dec 03, 2013 12:37 am 
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It has to do with wave tuning and pulse tuning to get the lengths of the port/manifold combinations to provide a planned short circuit allowing the turbo to spool its self. Much the same way the turbo f1 engines did of years ago. This allows the engine to become a power take off and not a power producer. I have calculated the engine to allow more boost pressure than turbo drive pressure therefore as the engine comes into overlap the ensuing fuel air charge not only packs the cylinders but also spools the turbo. The cam specs are as follows.

Image

disregard the "guess" that was early in development. I first set a goal of 200hp and my tweaking and tuning went from there


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PostPosted: Tue Dec 03, 2013 1:19 am 
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To save your self a ton of work you might want to have at look at the Suzuki Cappacino engines, the steel F6a twincam and the later all alloy K6a twincam, seems most of the big boost cappos are using the steel block F6a.
http://www.speedhunters.com/2011/02/car ... appuccino/


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PostPosted: Tue Dec 03, 2013 5:03 am 
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That's a neat article. Unfortunately much of that article I can not use, I can't have a 4v head and the engine is 800ccs well beyond what I could scoot through tech. Plus the availability of said engines is both pricy to import and I dont exactly want to cut up a head that I would have waited to get and would have to wait again to get another. I have looked into the crank and more than enough shops are capable and willing to make me a billet one. I choose this engine both for the availability and lightweight. I was originally thinking Kei car engines but since the Metro is the closest thing we ever got to a Kei car it fits the bill. I also like the 74-75mm bore it allows the combustion chamber a "better fill" than the smaller bore engines. If I knew the bore spacing of the smaller engines I was contemplating using the cranks out of them but again cranks in the 66-67mm range are still too much. 2" is only a 50mm stroke


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PostPosted: Tue Dec 03, 2013 9:15 am 
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How much boost, about 40-50 psi?

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PostPosted: Tue Dec 03, 2013 11:20 am 
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suprf1y wrote:
How much boost, about 40-50 psi?


That pull was indeed at a qualifying boost of 40 psi but its interesting to note the exhaust drive pressure never exceeded 35psi so its a seemingly livable cylinder pressure and its effectively keeping heat where it belongs in the exhaust to drive the turbo.

Image

Here is how the engine reacts to boost levels ranging from 25-40psi which is typical of setups ranging from a small tight twisty track with an emphasis on torque(25psi) to a typical race boost of 32-35psi and the killer I want that last 2-3mph down the straight 40psi for grid assessment.

Overall if I can figure out a few other aspects such as how to keep the head on the damn thing lol. I also see these are an open deck design and while I am not a proponent of block guards I am a proponent of block "pinning" where you strengthen the sleeve halfway down with an aluminum screw threaded into the bock up against the sleeve promoting better cooling and provides strength where its needed.


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PostPosted: Tue Dec 03, 2013 1:20 pm 
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It's nice to see someone else using the PT engine simulation...it's one of my favorites.
Regarding the suggestion of the Cappo engine, it is available at a good price here in North America, just watch for a wrecked Arctic Cat 660 Turbo snowmobile....same engine, and the CVT from the snowmobile might work for your car too. You are correct that it is a 4 valve head though.
I have run those engines up to almost 20 psi without anything but ECU mods, so they are pretty strong.


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PostPosted: Tue Dec 03, 2013 9:46 pm 
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I do enjoy the software as well. I use it daily for general quotes and to "prototype" design specs bofore I jump the gun. I have found this software very accurate. I am planning to have the prototype crank welded and ground using a stock core. This is going to be a considerable amount of weld but its just to test the dynamics of the complete turbo system. If I can get good clean pulls of say 200hp at conservative boost levels of say 15psi. I will be happy. If it hangs together I will crank on it till something fails and start from there. I have better feelings about the 3 cylinder vs 4 cylinder due to 2nd order vibrations which tear them apart when you really rev them. I struck a deal with a local Jy when I head to visit family for christmas to pick up 5 cores at 75$/ea. I am still hoping someone can chime in with some good Mk2 head port pics mostly interested in the exhaust port.

cheers


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PostPosted: Wed Dec 04, 2013 2:35 am 
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Can I ask why you would choose the Mark 2, over the Mark 1?
I'm not sure if you realize that the T3 uses a cast crankshaft...is that going to be suitable for welding/stroking like that? I would have expected that you'd get one of the crank companies to make a custom billet crank.

As far as porting the Mark 2 T3 head for a max effort project like that...I think you'll be breaking new ground.


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PostPosted: Wed Dec 04, 2013 3:00 am 
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It would take some searching, but I think I have seen cut away photos on here before.

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PostPosted: Wed Dec 04, 2013 3:46 am 
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Mr.Pipe wrote:
As far as porting the Mark 2 T3 head for a max effort project like that...I think you'll be breaking new ground.


Not entirely... it's just that Derek at Suzisport in Australia does not share any details about his small bore T3 competition engines, he wouldn't give me many details other than to say he was using 72mm pistons (940cc) and even with the very long stroke was getting a solid 200+ hp with low 20's psi, well that was about 5 years ago when I enquired.

Keen to hear what the billet crank is likely to cost since a 940cc T3 would allow me to move up and be at the pointy end of the 1600cc class, shorter stroke is definitely preferable to reduced bore, I did look at welding onto the crank to reduce the stroke by 5mm but am a little concerned about long term reliability.

Talking to the aussie guys making big numbers from the 4 cyl, block guards cause more issues than they fix, grouting half way up the bores seems to be much more reliable, arp stud kit is about your only option for trying to hold it all together.


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PostPosted: Wed Dec 04, 2013 9:34 am 
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Using 20-25 lbs of boost is an entirely different thing than using 40-50 lbs. The parts required to hold together in a road race application at 40 lbs would be quite special indeed.



Dattman said: Talking to the aussie guys making big numbers from the 4 cyl, block guards cause more issues than they fix, grouting half way up the bores seems to be much more reliable, arp stud kit is about your only option for trying to hold it all together.

After trying both of the above, (block guard and filler) with only limited success, I went with a method less used...in my 1.3 I use 72 5/16 long aluminum dowels inserted around my cylinders inserted into pockets machined in the water jacket...about 35mm long, and 5mm down from the deck. It has proven to be very effective.


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PostPosted: Wed Dec 04, 2013 10:20 am 
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I am glad we a some good insight and some thoughts getting tossed around. The "true" race engines will indeed be using a billet crank I have had them quoted in the range of 12-1500$ which really isn't bad as I am trying to get turn key engines in the 5000$ range after development. The first crank is more just to see how the rod to stroke ratio likes sucking on the port with that cam. I choose mk2 heads because I believe after working with bike engines for a while that the direct action OHC is a bit easier to get things not to float and to gut a set of lifters and make them solid is easier than having to reverse engineer a nice set of billet rocker arms for the mk1 head. I also like the vertical valves. The intake port I am going to raise the angle of the port from what appears flat to around 45 degrees and epoxy/weld in the required runner diameter which happens to be a 1.25" tube pretty simple the exhaust i plan to do almost the same but I want to do something about that water jacket. I guess until I get my hands on a head and cut one up who knows the exhaust runner in my model does have quite a bit less cross sectional area but I still would like to raise the roof and get a nicer shot out of the head. That being said the exhaust is going to get blown out anyway but easier path means a better flow coefficient and less heat stays in the CC.

I want to mention about what block mods will need to be done. I highly doubt the stock oil pump will even pump oil at 11K rpm and since little 3-4 stage drysump pumps can be had cheap this is the direction I feel to take. This also opens up the head as I can pump oil into and suck from it without having to use the stock feed or drains. If it turns out I need a crank girdle to keep the bottom end in it that too is not exactly a "giant" expense especially if it can be marketed to other members. The suggestions for holding onto the sleeves I like as coming from a honda crowd I have tried them all from devcon to guards and the pinning seems to promote the most cooling and best overall strength. I just hope the block doesnt end up in 2 pcs with the top half separated from the bottom. It appears to be just as strong in appearance as any other alloy offering from japan and the japanese know how to build good engines.

I am really looking forward to this project and cant wait to slap a big GEO sticker on the side of the racecar :D Even if it is a suzuki....

I am aware of the riggers of road racing people think because there engines make one pass down the strip and put on 1K street miles that there setup is "bullet proof" 2-3 laps at speed makes more heat and the stress of 7K+ rpm puts a premium on strong lightweight parts with an even bigger premium on cooling. This is one of the biggest reasons I go with a short stroke to keep the piston speed down and keep frictional losses ie:heat down as well.

I have jumped around a lot in this post but hopefully it all makes sense.

Any chance one knows how to ring the said tuner in Australia?

Cheers


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PostPosted: Wed Dec 04, 2013 11:18 am 
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I helped Derek quite a bit on those engines when he started building them, and sold him a bunch of parts. As I recall, he's not doing anything special, and was claiming 200 hp back then. I wonder how accurate that is.
Tim and Matt (MT motorsport) were making 200 hp with their T3 at reasonable boost levels, and not doing anything out of the ordinary. As I recall, though they weren't making any more power at higher boost levels, and that was with a Mk1 head.

I think you'll have to work pretty hard to get past 200 hp with that Mk2 head.

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PostPosted: Wed Dec 04, 2013 3:19 pm 
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I called my local crankshaft shop and while the first crank is not going to be cheap quoted around 800$ to weld and grind to that extent he did say it is feesable and is willing to take on the project. The crank will be taken to 2" stroke and a 1.770 rod journal for the Miata rods and either vitara pistons for the first engine or some inexpensive honda forgings. Now I am itching to get my cores...


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PostPosted: Wed Dec 04, 2013 3:56 pm 
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Why Miata rods?

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PostPosted: Wed Dec 04, 2013 9:58 pm 
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suprf1y wrote:
Why Miata rods?


an off the shelf solution to the massive reduction in stoke coupled with the Vitara pistons which to accept the rods will need the wristpin bores honed out 1mm to 20mm

That's one route
For less work at slightly more expense I could use Honda d15 rods at 134mm with d15z1 pistons and have the right wristpin diameter.

Or I could alter the stroke just enough to get either combo to work with well either combo. The pistons have nearly identical dish volume with only compression height difference of roughly 1 mm


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PostPosted: Wed Jan 22, 2014 6:00 pm 
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I'd like to see where this is going. If you can make that kinda power. Please fill us in. Enquiring minds want to know.

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