What turbo do you have now? Where do you see full boost and how much PSI do you run?

I am a turbo guy, my Audi 1.8T's KO3 I replaced with a GT28R, which I replaced with a Comp Turbo CTB5356.
The KO3 is to small of a turbo for even just the 1.8t, Full boost under 2k, Boost starts to taper off after 5k, Shift at 5.5k Max power ~ 160AWHP (20psi).
The GT28R was a perfect sized turbo for the 1.8T as an autox'er or daily, Full boost under 2500, boost doesnt taper off even at 7200rpms shift at 7200 rpm's every time, max power 275AWHP(20psi)(This turbo gave INSTANT full boost above 4krpm's, aka any situation in an autox.).
The CTB5356 is a bit large, but with the increase in turbo technology its a very good sized turbo for daily driving, however a tad laggy for instant boost at autox. I would consider this an awesome track turbo. This turbo is designed to run extremely high boost pressures (35PSI) and still be efficient, which was the reason why I chose it. I run only 10psi at the moment and it makes the same power as the GT28R when I ran 20psi. Full (Low) boost ~4krpm, probably 4500 at high boost, boost probably wont taper off till 8500 rpms but my tune doesnt go past 7200 currently. I anticipate well over 400AWHP(25psi) when I crank the boost up. If I ran C16 and spent some time on the head I might see 500AWHP(35psi), but I dont think I'll get to that point any time soon.


I am a big fan of the right sized turbo for the job. You might want to look at the SR20DET turbo's that come stock. Some of them are ball bearing, but most are journal bearing and can be had CHEAP.

Small turbo's make excess heat. Excess heat means detonation. Get yourself a nicely sized turbo. I wouldnt throw a KO3 on anything more than a 1L Geo engine.

Also Audi TT's (225hp model) used a KO4, the 180hp model used a KO3. The KO3 has stopped being used in most engines due to its small size, the KO4 is almost the exact same size but is more efficient, however more desirable. Consider that if you REALLY need to go with a small turbo.

http://www.914world.com/bbs2/index.php?sho...lutch&st=20

In my review of 2012 I don't know how I forgot the crazy clutch adventure.

Andyrew- thanks for your input on turbos. Yes, I agree, the right tool/turbo for the job, and I agree, smaller can = more heat. The intercooler set up I have, while unconventional, shows no more than 25-30 degrees above ambient temps for IAT, and for the short duration of an autox, I'm fine with that. I could always add water injection if needed, or go to an air-water set up. I've had experience with both.

The thing that is most vexing here for me is the airflow thru the engine. Even with Lens great heads and Jakes much upgraded cam, there just doesn't seem to be alot of flow to work with. I think its a combo of the 2 valve heads vs the 4 and 5 valve heads of more modern cars, along with the length of the exhaust system. STS with their rear mount turbos makes it work with a much smaller turbo than conventional wisdom would suggest. So what works better on your 1.8 5 valve TT head may likely be all wrong for my 1.8 2 valve rear mount turbo system.

For me a bunch of the fun is in the tinkering. So I may be looking for a good K03 or K04 to play with some more.

The K03 and k04 are great little turbos! The only issue is their hot to cold side sizing. This would be my only disagreement with Andy. The K03 was optimized for the 1.8 due to the unsquare engine design. Reason being they needed torque out of a smaller displacement. You have an 80mm bore and 86mm stroke. This means you need a little volume of air really fast without huge boost numbers. Granted, this turbo will not last long when ran hard, but the way it was designed it will be reliable. This turbo will produce 12-18 lbs paired with similar volume (meaning exhaust gas CFM to intake volume). The way you Would ultimately pair a turbo would be based not only on efficiency of displacement to turbo but also volume needed (volume of cylinders/intake) to volume produced (cold side) to volume created (after engine firing headed to hot side). There are better ways of wording it but this gets my point across.

My graduation project for my high performance class was building two NA engines (2.0zetec, 2.4ecotec) with turbos. I ran a number of tests to optimize stock (junkyard) engines & parts. I was very lucky to have a teacher who was very well versed in the forced induction world and willing to teach a punk a$$ kid like me.

To sum up, all of the type 4s are that the opposite of what a normal turbo engine "would" be. We are dealing with large bores and short strokes. So with this said you would ultimately want to find a turbo that matches this "backward" design just the same. The volume of air coming out of the type 4 in exhaust gas is low pressure and in short spurts in comparison to a typical turbo engine by design. So increase the size of the hot side by trim not by housing volume. This will allow more movement of the turbo earlier to maximiize the low end, but the waste gate will be working OT in the upper rpm to bleed off the unwanted pressure. But let's be honest, we aren't revving these little guys to 7-8 rpm under boost.

I know it is a lot of information, but I have been through this and I agree that tinkering is an absolute blast!

Ottox I have a 13b turbo that has been rebuilt with a little shaft play but very usable if you'd like to try it, I think it would be a great match for you. I have really enjoyed your thread and I admire your work. Hope to see this car one day!

Better late than never? I finally got out to my father in laws farm for a few pics of the current supertrap muffler set up. I know its not as free flowing as the straight pipe was, but it seems to flow pretty well just the same, as it is basically a straight thru system. And the small reduction in sound is appreciated. At WOT in 2nd gear I've blown high 80's db at an autocross, and with some of our sites at a 94 or 96 db limit, I'm right where I need to be.

Andyrew: Good to know about your positive experience with the GT28r on the TT. If/when the turbo on my TT pops I know which direction to go now.

tscrihfield: I've wondered about something just like this, as I have been puzzling thru the project. In all the books I read researching this, and later internet surfing, I don't recall running into a discussion of the bore/stroke being a consideration in turbo sizing. Maybe I just missed it, but what you said is just about exactly what has been nagging at the back of my mind for a couple yrs now. So accepting your position that the b/s configuration of the motor will have a direct effect on the onset of boost for a given turbo, all other things considered equal, what would your opinion be of a correct turbo for my engine, a 1.85L 4 cyl with a b/s of: 90/71, and why. And if you would, get into more of the specs of the turbo you have on hand, what cars it was on, and why its a better choice for my engine. Oh, and would the K03/4 be a decent choice according to your thoughts. Funny, I always thought of the 1.7/1.8 motors with the 66 crank as the "short stroke" motors, and now it seems my "stroker 2.0" 71 crank really isn't all that long... My "small" turbo was a 9b, one of the 2 turbos on a mitzu 3000GT. The turbo that is on the car now is from a subi 2.0L wrx. It seems to make good power from mid to high rpms, once there is some airflow, but I wouldn't mind the onset to be a little sooner.

Fun stuff! Thanks for adding your info to the thread.

Haven't run it yet...

But mine is a K03. There is a K04 that I should be able to jump to if this thing is too small, but I think we had the same thought process, "If it's on the small side for a modern 1.8 with modern CAD optimized flow, it might just work great for an old design Type 4." Mine is a tired, stock 1.7 though, so where your engine may slightly overwhelm the K03, I'm hoping my low flow engine will be perfect.

Who knows! One way to find out...

Mark is that an OEM ko3 or a Chinese version?

If its chinese, just realize spool with not be as quick as it should be. Be sure to run oil though it without firing the engine (aka remove the plugs and keep cranking, let starter cool and do it again...)

He has a real KKK K03... Ask me how I know... The one pictured is not it...

Fun thread, ottox! I noticed your Direzza Star Specs in the photo...one of my favorite tires.

Is the T4 much different than the T1 at the cyl/head mating? I did a turbo on my T1 and put some of the soft copper shims to lower the compression and figured it would get a better seal. No problems and those engines get turbo'd alot.

Hey Mark,
I have a question before I delve too deep into opinions. Have you ever had the heads flowed? Knowing the CFM on the exhaust runners helps but not necessary.

I have played with a few Numbers to calculate what I think might help. That engine is capable of moving somewhere in the neighborhood of 430 CFM max. This is assuming your heads flow at 1:1 rate with ability of volume able to move and have no restrictions in your intake/exhaust. The one big issue with this assumption is pressure will have to go somewhere if it does not exit through the exhaust. if it cannot go out the exhaust smoothly it will escape during the valve overlap period therefore pressurizing the intake while the turbo is trying to feed pressure in. This will cause what is known as compressor bind. If it is not audible it is a bear to hunt down and a lot of folks never know they have this issue when they have it.

I want to also state that the cam plays a part as well. But I will leave this out for lack of more overload.

Now we are still playing with a vacuum pump but the information I have gathered is this (and this is my theory behind the B/S difference). When I refer to this difference it is in leiu of the typical person trying to size the turbo. The only time you have a greater amount of CFM ability loss is when your bore exceeds stroke and this is what throws off so many folks CFM predictions (your simply dealing with a different beast). I don't have all of the answers behind it but my guess is that it has to do with common physics. Larger volumes of air are trying to exit the cylinder at the same time whereas a smaller bores with larger stroke has smaller volumes of air exiting the cylinder at that moment in time. If I was hosting a webinar this would be easier to demonstrate because I lack at conveying messages by form of writing. Non-the-less I hope you get it.

I would stick with a turbo that moves less CFM through the housing than your engine produces, remember you can always bleed of anything you don't need. This will allow the spool to happen quicker and peak faster. The one downside is heat. Now the good thing about this is you can go with a smaller housing with the same trim and see huge improvements with your current setup. The current turbo you are running is known as the TD04-13T. The turbo I have is the TD04-13G the biggest difference is Volute size which directly changes CFM flow. The 13T is rated at 385-400CFM and the 13G is rated at 345-360 CFM. it is originally off of 1G eclipses. My advice in any application with these cars is to run an external waste gate so you can get proper boost and bleed off the heat. But for both of these turbos you can get away with the stock waste gate built in the turbo and be fine, just don't crank them too high.

On the K03 it will actually flow less than the 13G and the 9b would be about the same. the K04 will flow about the same as your current turbo. I do agree with Andy on the SR20 turbos. Stay away from the base T25 turbos they are looking for too much volume and their journal bearings suck. The later 90's T28 had ball bearing but still a .80AR and 60 trim. This would spool a little later than the 13G and sooner than your current turbo but peak quicker than any above mentioned.

Please feel free to ask me anything on this. Most will be dialing in to find what the engine likes. I love this thread and it looks like you are on the right track!

Thomas

McMark- get that thing in a car asap and let me know how it goes, and if I need to fund a K03 for my car.

I tired of doing all the R & D around here...




tscrihfield- Thank you for your post and insights. Just enough math to make your point and keep it interesting, not so much as to melt my limited brain cells.

So being as my 13T and your 13G are close cousins, can I expect the 13G to bolt right in place of my 13T? And if so, how might I get your 13G up to my place this spring? Do you ever have to travel for work to the twin cities area...

So far as airflow thru the motor, OUR (me, Len Hoffman, and Jake) thought process was that stock sized intake valves, would promote more velocity into the head at low flow/pressure rates for better cylinder filling and off boost performance, and that the turbo would push in as much as would fit once things got cooking along. The intake/exhaust ratio is around 85% as I recall, so there should be about as much flow out the exhaust as possible with out compromising the head castings. The exhaust is a standard kerry hunter 4:1 system. I'm not sure of the size of the tubes, but they are not gigantic. I don't expect to push much more than 14psi thru the motor, so lots of pressure is not in the cards. I'd just like to get to that 14 a little sooner.

Any thoughts on why the 9B would have been such a poor performing unit, barely able to make 5-6 psi, and all of that on the top end, vs the 13T making 12-13psi at top end, and spooling up nicely? There were NO changes to the car other than just swapping out one turbo for the other. How closely spec'd are the 9B and 13G?

I almost forgot to tell you that all of my CFM calculations were based on your engine @6000rpm.

On getting the 13g to you, I could ship it. I was just in Minneapolis a week ago... I may be up there in a month or so, but not sure yet. This is the turbo inlet...

And the outlet...


Knowing your efficiency in your heads tells me that the flow of your engine will be 365-370 CFM. This would explain the late spool for the 13T.

For the 9b, it sounds like that little guy was being worked to death! That turbo would have hit max boost when your engine hit 3400 rpm. After that it would have been fighting itself. That little guys max flow is 265CFM. The 9b is far away from the 13b by nearly 100CFM capability.

Thomas

Back again. Started a new job in Feb, and getting my feet wet there has taken up a bunch of my time. That, and the cold, damp, no-fun weather in my neck of the woods have not encouraged garage time.

ANYWAY, thanks tscrihfield, (Thomas) for your info, and the offer of a turbo. Sent you a PM on that. Speaking of, anyone have any flanges that would work with the pictured turbo? The exhaust side is interesting, as depending on the flange, it looks like you could do a divorced waste gate set up. Hmmmmm..... interesting. More pics would be nice, of the turbo itself, so I could see what the options are to clock the housings to get the right orientation for my application. I'd be curious to see some of the maths used to determine the application of one turbo over another, and how the K03/K04 twins would fit as potential options. Any additional specs of the engine you would need for better calculations? If you need a couple bucks for the turbo, lets talk.

Dave

Thomas has generously offered up the turbo pictured above for "development" purposes on the 914 turbo project. Don't know how soon it will show up, or when I'll have time to goof around with it on the car, but I'm excited!

I'll keep the updates coming as progress occurs.

Any Updates : )

Please see attachment

Man! I just got rid of my VF31 and VF 32. The 32 probably would have been perfect.

the article is in my blog

jim

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It's been done before get a copy of June 02' Excellence magazine 2.0 4 cyl. w/CIS injection and a K 26 turbo still runnning strong
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