Turbo, small T4 and the stock cam,

MattKab · Post by **MattKab** » Sat Jan 07, 2006 2:56 pm

I am nearly ready to assemble my T4. While I'm holding out for serious parts for a 'bigger' other engine. I'm trying a turbo 1.8, nearly all stock, only after about 7 or 8psi, 5500rpm max. Garret T2 I'd settle for ~135hp

Car is '79 Karmann, will be ~1150kg with me and T4 installed, trans is stock ratio AT with ZF 3250rpm@70mph, 5000rpm@100mph, intended use is Nürburgring (Transcontinental, long distance/high speed/corners).

This engine is temporary and for optimising my T1/Cali cooling, etc. The case is in great shape, I might use it on my 2056 later on.

I have 2 USED stock cam and lifter sets, both are 1974 1.8l T4, 1 is US L-jet and other is UK twin 40 solex..1 is going in this engine in the next week or so. No rush.

No ugly wear patterns on the lifter faces, cam lobes. All indexed to bore.

I'm able to measure and plot the profile of the 2 cam's in crank degrees against lift at the lifter, but I've never chose a cam for an engine. I've built 7 stock T1 engines, with stock cams....

If I see less overlap on 1 cam, I go for this... right? Not that I'm expecting anything remember.

I know the script goes web cam and lifters from Jake but this is sweet cheap practise engine.. All parts to build the bottom end are poshiled/checked/very clean. All new bearings/Curil K2/11 galley plugs/AN-8 oil lines, AN-3 to turbo.

My head choice is T25 with new valves, will go for 41*38 or even 40*40. Petrol is 97/98 RON. CR is undecided.

Opinions please, will it melt? I have 10 channel data logging inc. 4 channel EGT and LM-1 to tune single TB/plenum 2bar MSnS Extra code and EDIS.

I wan't to avoid any need for a cam break in until the rest of the conversion is proven (to me).

Rods and bolts are stock, new big-end shells are Mahle bronzina from Brazil. Same as the mains.

I need some feedback on my plan, tear it apart at will. Is there an obvious cam for this combo? Web 73?

Matt

Eddie Brown · Post by **Eddie Brown** » Sat Jan 07, 2006 11:30 pm

Sounds like a fun project. Less overlap is a good thing...stock FI cam should work nicely.

Good luck.

farmer · Post by **farmer** » Sun Jan 08, 2006 11:47 am

Matt. In your case, I would opt for the cam with the most overlap. Many yrs ago I made a rough "dial" on the difference of the T4 cams, and came to the same conclusion as written here. The "E" and the "S" cams are so close to alike that it hurts.
As stupid as one is somethimes, I never got the data written down on more than a piece of the latest newspaper. And guess where that ended

You will be able to find variations within the stock specs. - Again, use the cam with the most duration, if you spot a difference...
135 hp @ approx.9 psi is absolutely possible.
T.

MattKab · Post by **MattKab** » Sun Jan 08, 2006 2:14 pm

Thanks T., I value your input. I'd like to know the spec on those other cams

I carefully measured 3 stock Bus cams today (exhaust only), plotted them together, put them in a new thread.

Matt

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon Jan 09, 2006 8:39 am

Heat is the killer.. ALL stock cams were designed to help with the engine's warm up times through a bit of heat retention.

I have been doing R&D work with 100% stock engines+ Turbo for a few weeks already as I design my Turbo kits for TI and 914 applications. I have found the weaknesses already.

More engines will be painfully compromised on purpose in the future as well! I have 3 more to kill before the end of this month!

Jeza · Post by **Jeza** » Mon Jan 09, 2006 6:20 pm

MASSIVE TYPE IV wrote:Heat is the killer.. ALL stock cams were designed to help with the engine's warm up times through a bit of heat retention.

Can I ask how a cam retains heat?

I'm sure its an obvious answer, but if I don't ask the question I'll never get the answer

I'm looking forward to reading of your T4 turbo testing Jake.

Its great to see so many low budget approaches happening now as well.

Thanks
Jeremy

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon Jan 09, 2006 6:31 pm

The cam dictates the events within the head- a cam with crappy specs can promote hot heads, it happens all the time.

MattKab · Post by **MattKab** » Mon Jan 09, 2006 6:42 pm

HEAT is what I'm living to beat Jake. Have fun bursting those old motors.

I found the ground-down remains of the carb cam to have more duration and lift than the remains of the FI cam, both are split-duration at .020" and equal at .050. The carb cam has 2 degrees less lobe seperation angle.

The carb cam will move the heat along quicker. ..? The exhaust valve opens sooner, closes later. Inlet valve opens sooner, closes later. Exhaust valve reaches max. lift 4 crank degrees later..

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon Jan 09, 2006 7:01 pm

Any stock cam is far from optimum, this is clearly illustrated by the 15-20% gains I have logged with only a cam swap in a 100% otherwise stock engine all while running cooler and getting more MPG.

Vielzidub 3 · Post by **Vielzidub 3** » Fri Feb 03, 2006 2:25 am

MASSIVE TYPE IV wrote:Any stock cam is far from optimum, this is clearly illustrated by the 15-20% gains I have logged with only a cam swap in a 100% otherwise stock engine all while running cooler and getting more MPG.

Was that with one of your spit duration 'custom' cams or a more traditional 'tuning' cam?

I have always beleived what I read in the Dellorto tech book with regards to split duration cams. In my opinion their potential is commonly overlooked by tuning manufactures, I guess because there applications are so specific to an engine combination.

Good to see you are making them Jake! Shame you can't reveal their specs.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Feb 03, 2006 7:14 am

Almost all my cams are split duration.. 36 of the 45 cams I have designed or tweeked from other cams are split!

With the TIV if you are not using split duration you are cheating yourself out of power and cooler running heads with more MPG!

70dragbug · Post by **70dragbug** » Fri Feb 03, 2006 1:38 pm

MASSIVE TYPE IV wrote:Almost all my cams are split duration.. 36 of the 45 cams I have designed or tweeked from other cams are split!

With the TIV if you are not using split duration you are cheating yourself out of power and cooler running heads with more MPG!

Is that due to the type 4 exhaust port being more retrictive than the intake? From what I´ve heard it´s even more evident on type 4 head oval ports than the bus head square ports.With a split duration do you mean a longer exhaust duration than the intake duration?

Vielzidub 3 · Post by **Vielzidub 3** » Sat Feb 04, 2006 9:43 am

MASSIVE TYPE IV wrote:Almost all my cams are split duration.. 36 of the 45 cams I have designed or tweeked from other cams are split!

With the TIV if you are not using split duration you are cheating yourself out of power and cooler running heads with more MPG!

Note taken! This must be the case for type 1 engine set ups too then, even if to a lesser degree (excuse the pun

) This was as I suspected, since inlet sides of heads are designed to do totally different things to the 'zaust side. I mean look at stock valve shapes! Never quite understood why stock cams and certainly tuning cams were not split duration as standard myself.

Anyway since you have the evidence to back it up and have a good selection of Split duration Type 4 cams, I will have to seriously consider one.

Mybe I will wait until your cheaper upright cooling system come avaialble so as to be able to make up your minimum order (although I was loking forward to all those hours making the metal fit the heads etc. . . if I can ever find a second set of 2L 914 head shroud metal

)

Not sure on which engine it would be for yet! What are your opinions on these? Do you have a cam specifically matched to one or the other (or both?)

71mm x 103mm = 2366 vs. a 66mm x 96mm = 1911.

Both would be using stock cranks and rods, and the 2366 would be using some reworked 38 x 48 vavles, and the 1911 stock sized (maybe +1mm) 2 litre 914 heads.

Cheers,
Dan

type3 · Post by **type3** » Mon Feb 13, 2006 2:40 pm

Hey Matt,
Have a trawl though the archives and see if you can find posts by Evill Ed. He used a Webcam #73 in a 1800 (IIRC) with good results. That's also the same cam that Jonas Linder on this forum is using, would be worth talking to him too. Just a thought.

cheers,
type3

fuey22 · Post by **fuey22** » Mon Feb 13, 2006 3:33 pm

talk to marty staggs. he has built a few type4 motors with tubos. stock 2.0 ltr.didnt change anything just added a turbo says it works awesome but for a build he suggested a cam with 112 lobe center for me it was the webcam 86b on 112 center