Turbo for a 914..., this may work Options

[Jake Raby]

That stock cam is the big limiting factor, since it bleeds so little CR away..

I'd run no more the 6 PSI to be safe...

No head gasket is gonna help ya here...

I'm working on an inconel filled O ring for the cylinders to cure this issue, but only testing will show if it will work with a cast iron cylinder. They were designed by Porsche for the 102mm cylinder which was of course aluminum..

Its worth a try!

[mattillac]

any cam suggestions to help? 6 psi seems like such a dull number. is 9 to 10 psi really unreasonable?

[Jake Raby]

That cam really does suck..

How are you feeding this puppy??? What EFI or carbs??

[mattillac]

i've been looking into megasquirt pefi with ignition control. i'd like to get some feedback
from experienced turboer's before i invest my time and hopefully not too much money into a turboed teener.

[Joe Bob]

Dang sorry about the rant - MikeZ knows how to turn my knob I guess! (IMG:style_emoticons/default/biggrin.gif)

HUH? (IMG:style_emoticons/default/blink.gif)

What I do??? <_<

My Vortech Blower runs well on my Mopar 360....it's in a sleeper Dodge Dakota and runs about 8psi normally....except for the shittyass gas mileage it runs great. AT about 70 on the freeway...I can click the electric ODrive off push up the boost controller and that thing puls like a strippedass ape up to 140mph.

I love it when some yokel rides my butt on the onramp and I pull away like he was stuck in a mudbog.

I'm sorry I have to sell it....too many cars and trucks and now that the remodel is "almost" over....I need to thin the herd.

[Brett W]

Yeah the stock engine is not raelly suited for the turbo upgrade. You might look into running a CIS unit for ease of fuel delivery. A built stock motor can handle 14 at most. After that the heads start flexing and then you get really cool things (or not so cool).

I am planning on running 15 on a daily basis but it ain't and aircooled engine either. Supercharged boost levels and turbo charged boost levels really have little in common. In my opinion there ain't much point in building a turbo setup to run anything less than 10psi. But that is what makes this a great country. Opinions. (IMG:style_emoticons/default/biggrin.gif)

[Mueller]

If you guys are driving these things lower than 2k/rpms.... I feel sorry for ya..

That's my point. There is only lag below 3,000rpm and since durring any spirited driving I'm always above that, I never experience lag.

As for longevity, head leaks, etc. Well, I built this on a 1.7 which should give me the best head sealing I can get from a stockish typeIV. The total turbo install cost me $175 (I'm a Root/Malmz sorta guy (IMG:style_emoticons/default/welder.gif) (IMG:style_emoticons/default/aktion035.gif) ). If the engine goes I won't shed any tears. It's been way too much fun already. I'll drop in another $250 1.7 and do it all over again. Unless I've already dove into a Subaru turbo conversion before this motor lets loose. In the mean time I'm going to keep smiling because this thing is a riot.

-Ben M.

my turbo install is similar to Bens, cheap and if something goes "boom", not a big deal...motor cost was 250 and the turbo was 250....i'm not looking for it to produce exhilerating hp numbers, I just want a little more so when i do drive the car to work, I don't get passed by diesel trucks going up Vasco Rd (IMG:style_emoticons/default/wacko.gif) (not sure of the incline angle, but I have to drop down a gear in all of my vehicles except when driving the 911 just to keep going the speed limit)

[andys]

Well, that Crown Engineering drawing brings back some memories, for sure! That's the one I had on my '73. Yea, I never liked that boost controller either. I found it better to control boost with mild exhaust restrictions if the turbo was sized properly.

Keeping boost around 6-7 psi is a nice balance between reliability and performance, IMO. As you go higher, the diminishing returns of stressed components, spark timing management, fuel management, etc, become extraneous requiring a purpose built motor. Those high boost Japanses motors were built to take it from the start, along with the appropriate management systems and intercoolers so the comparison is apples to........ Sounds like Jake has done some TIV turbo work; nothing like experience to get a real handle on things. Also, don't loose sight of the fundamantals.

No lag at 3000RPM? RPM doesnt matter nearly as much as load. If you were travelling down hill at 3000 in a no load condition and nailed it, you would get lag. I'd look at some type of bypass valve to help on-again throttle response. FWIW.

Andy

[mattillac]

well i have to do a valve adjust every 3,000 miles, so i'll just retorque the heads at the same time, every time. (IMG:style_emoticons/default/huh.gif)

[ClayPerrine]

well i have to do a valve adjust every 3,000 miles, so i'll just retorque the heads at the same time, every time. (IMG:style_emoticons/default/huh.gif)

Better drill holes in the upper tin and get plugs for them. Otherwise you can't get to the top head bolts.

[Sammy]

Whoa, whoa, hold on a minute.

before we all contribute any more to an urban myth, let's clear something up.
There are two very different things we mave managed to mix up here, turbo lag and boost threshold.

Lag is the time it takes for the turbo to spool up enough to develop boost pressure (when in boost threshold).
Threshold is the rpm range of the engine at which a turbo system will develop boost.
They are not the same thing at all.

Even at 6000 rpm at partial throttle, it will take time to build boost pressure when the loud pedal is mashed. Hopefully not very much time, but there will be a delay. THAT IS LAG.

If you nail the throttle at 1500 rpm, you wont develop boost until the engine revs up to a certain point, usually anywhere from 2500 to 3500 rpm. THAT IS THRESHOLD.

Early 930 turbos are notorious for having excessive lag, but that is not entirely correct.
A large part of the blame should be put on threshold which is exaggerated by the extremely long gearing of the 4 speed transaxle. It takes a long time for the engine to rev up into threshold so it can build boost. That isn't lag at all.

Having a remote mounted turbo will work fine, but the extra length will add to the lag a little.
It takes time to pressurize a pipe. The longer the pipe, the longer it takes to pressurize it.
While the threshold will only be increased slightly, the lag and the time it takes to build full boost will both go up.
Prolly not enough to stress about, but they will go up.
Longer pipes mean cooler pipes unless thay are well insulated, cooler (exhaust) pipes means less energy and efficiency, but again proly not enough to stress over.

I see nothing seriously wrong with their product, it prolly works fine but I cracked up when I read some of the marketing BS on that web page. They claim that the remote turbo system is as efficent and has no more lag, but then they turn around and say the turbo runs 500 degrees cooler. Who are they trying to buffalo, a bunch of spikey haired Honda drivers?
Real gearheads who understand turbos, and anyone with half a clue about physics will see through their BS in a second.

I ran my type 4 turbo at 6 to 7 psi all the time, occasionally at 9 psi (which the engine didn't like as much, too much heat) without any head gaskets installed and never had a head leak.
I did lap the surfaces together on assembly that's all I did.
I must have been lucky. (IMG:style_emoticons/default/aktion035.gif)

[Jake Raby]

A retorque of the heads isn't what will cure it..

Its a design issue, and material issue that is intensified by boost......

Retorquing the heads, especially tighter than stock will make the issue worse....

[mattillac]

A retorque of the heads isn't what will cure it..

Its a design issue, and material issue that is intensified by boost......

Retorquing the heads, especially tighter than stock will make the issue worse....

i read in a tech article somewhere that it's good to retorque the heads to spec when you do a valve adjust. don't know if that is really necessary, but it didn't seem like it would hurt anything. (IMG:style_emoticons/default/sad.gif)

[Sammy]

6 psi boost is not boring, it is very fun and very surprising. 7 is more fun, anything much more than that is pushing it unless it is engineered very well.
Drive a type 4 with 6 psi boost before forming an opinion.
Don't get into the ricer trap of more is better, bench racing doesn't do any good with turbos and type 4s.
The stock type 4 cam is very well suited for a turbo application because it is so mild and had a relatively low overlap. Turbo engines don't like wild cams.
With a turbo at 6 psi boost and a stock cam a 2 liter type 4 will happily rev to well over 6000 rpm without falling off. It will pull hard until the valve springs float so it takes some discipline.
First time Mikey rode in my turbo at an AX he asked, "doesn't this thing have a rev limiter"?


Re-torquing head studs after the engine has operated for a length of time is...... well it isn't accurate.

Torque in this case is the amount of twisting force required to put a predetermined stretch on a fastener and is EXTREMELY dependent on friction. It isn't how much you twist, it's how much you stretch the stud that really matters.

When you build an engine you put some sort of lubricant on clean head stud threads and the washers, right?
When you retorque the head studs do you take the nuts off, clean all the threads and washers and apply new lubricant?

I have a spreadsheet put out by HYTORQ that lists friction factors for many different type of thread lubricants, even for dry.
According to the spreadsheet you would have to use almost twice the torque with clean dry threads to acheive the same stretch as when using never-sieze on clean threads. If the threads are rusty, that number will skyrocket. If you get peace of mind by doing it, great. Just remember that the numbers you are using are basically meaningless and won't do a bit of good except maybe tell you if a head nut came loose.

[mattillac]

thanks for the info, sammy. i'll save head torquing for a rebuild. the difference between
an old and new bolt/nut is something i didn't really think about.

[Sammy]

I should clarify something, on a six I would recommend "checking" the torque on the head nuts every time you have the valve covers off, just in case you have a stud pulling out (mag case) or have a dilavar stud break (3 liter on). You wouldn't be checking to see if the stud is torqued to spec but would be checking to make sure it didn't come loose for some reason. I suppose the same thing would work on a type 4, but I haven't personally had any type 4 head nuts come loose and I haven't heard of type 4 head studs breaking so I don't know if there would be any benefit. It wouldn't hurt anything except maybe the skin on some knuckles.

[airsix]

I'm just going to have to make a video and/or take a few of you for a ride. Sammy's right on all counts. The final word on my turbo is it cost $175 (+$500 PEFI already on the car) and it's an absolute riot.

Restating some of the specs after reading Sammy's posts:
Boost threshold is 2,300rpm
Lag is there but not an issue.
At a steady 3,000rpm cruise you can nail the throttle and boost is almost instantanious, peaking by 4,000-4,500rpm.
Already have a blowoff valve, and it works great. $19 Saab OEM "overrun valve" from FLAPS. Even makes that nice mid-shift "PPPSSSSssss!" noise the kids all like.

-Ben M.

[Joe Bob]

First time Mikey rode in my turbo at an AX he asked, "doesn't this thing have a rev limiter"?

Yep....cheap bastard refused to buy a aftermarket CDI.....

[Brett W]

There was a 95mm Ni-Resist ring available for the 930 engine I beieve. If you run it you should mill a receiver groove in the cylinder.

Boost is a measure of restriction nothing more. What is more important is cfm and pressure ratio. If I run 10psi and flow 500cfm the intake charge will not be heated as much as it would should I have to run 15-20 to get the same numbers.

Turbo engines like lots of Lift, which the stock cams do not have. It really doesn't have enough duration to make a good turbo cam either. The Lobe centers are also wrong. The stock cam sucks.

Most of the turbo kits can't handle extended boost runs. While most homemade kits are good for an autocross or short highway run they can't handle running bosst for an extended time. If I remember correctly Sammy's yellow car would overheat the oil after anything more than a short autocross run. This coming from Mark.

I am glad you turboed a 914 and I am glad it is working for you well. I personlly can't see doing all I would have to do to a T4 to make it a boost happy motor. Not worth all the trade offs and limitations.

[Sammy]

Hmmm, I guess you've been reading different books than I have.
According to Bob Tomlinson in turbomania (a book about turbocharging air cooled flat 4 engines) he states that long duration is a negative because it allows some of the charge to go out the exhaust with no benefit. He says anything over 270 degrees is too much. Corky Bell agrees with that statement in principle. I can't say much more except I've BTDT with good results.

BTW I never, ever had a problem with the oil getting hot in the turbo and I ran it much harder than short AX laps. I never, ever saw the temp guage get near the red zone. Maybe it did for Mark, I'll have to check with him on that. Last I remember he did say that the oil temp got near the red mark during a rally in the middle of a very hot Atlanta summer. That is the only time I ever, ever heard of that engine getting hot. If he was having problems he didn't mention it.
This car did not have anything more than a stock oil cooler. Maybe if you increase the horsepower a bunch you might need an aux. oil cooler? Big surprise there, who woulda thunk? He and I discussed that very point before he bought the car. It was one of those things I eventually planned to do but was in no hurry because frankly I felt it did not need one in so Cal.

Can you provide some information to what you used to make the statements on the cam? Particularly higher duration and lobe centers as it applies to air cooled flat 4 engines. I'd be interested in reading that.

Heat generated from boost is heat of compression. Nothing more and it is not flexible. it varies only with density, humidity, etc.
Obvoisly 10 psi will generate less intake temperature than 15 to 20. I don't see your point there.

Have you driven a turbocharged 914 with a type 4 engine?

Others have done it with great sucess, they used the stock cams and had very boost happy motors.
If it works it works.
I'm a little confused at your statement that it takes too much to make a type 4 boost happy. Can you provide more details of what you think it takes?
Granted you can't make a type 4 like a twin turbo supra engine or nissan skyline, that isn't the point and only a fool would even contemplate such a concept.