C/R with Web 86 cam ?

[farmer]

What is safe CR with that cam in a 2 l. T4 with flat top pistons, 2l. square port heads, std Leistritz muffler and fed by twin 40 solex ? All residing in a type 3 Variant.
It is now 9,3 -1, but pings bad under load, even with slightly retarded ignition 26-28 Btdc max advance. Temperatures are on the high side too.
Torben

[MASSIVE TYPE IV]

When I used that cam I ran a max of 8.3:1 with it.

I tried 9 but it would not work, even with super tight deck and a really good set of heads..

[farmer]

HUUH ! I´m in trouble. So what youre saying is that this cam do not like more CR than a stock E, S or 914 cam (?) Perhaps even a little less. (I´ve done just under 9-1 with stock cams on super unleaded gas with no problems.)

- Is there an alternative in that duration range, that does like higher CR ?
T

[BigOlJohnson]

You could probably get by with more CR with a different set of heads.
The chamber design of those heads create heat!

Did you unshroud the valves?

That would get you about .5 CR reduction without increasing the deck.

What IS the deck? Shoot for .045 and increasing the head's CCs.

Don

[farmer]

The deck is 0,044". Valves are already unshrouded, due to the fact that this particular engine has been detuned. It used to have a split cam (the wrong way) 250/242 @ 0,50" "because " it was run with the 40 solexés. But it was hysterical. Idled awfull, had temperaure issues, and litterally was a pain below 2500 rpm. But pulled hard above 3K - Now it idles fine, but have pinging and temp issues. Not much better.
I think I may have to dish the pistons.-
How much is safe to dish a Euro 914 piston ?
Other solution could be to do a mild hemi cut, but I´m not fond of that.
T

[Piledriver]

EXACTLY when does it ping, and when is it hot?

First thing to try is see what timing/jetting it REALLY wants.
(might require better gas or octane booster for testing)

You might also try one or 2 size larger idle jets, assuming it's light throttle (cruise) hot+pinging or on transition. AT WOT of course its mains or ACs. (Richer mix does NOT always == poor fuel economy, up to a point the opposite occurs, with cooler running)

CSPs calculators say you have ~51 cc chambers, all else as you described.

On the Pile, ("stock"1700, "Q" heads, domes. ~.030 deck, ~8.6:1, CIS) I have experimented using as little as 22 degrees total timing (+ vac advance) with little to no issues, as long as the timing curve is tweeked to compensate, (still >12 initial, starts advance at ~1200) and over 4K it actually pulls much BETTER.

(I have an oiling/carbon issue on #4 that is about to be resolved--worn out jug, hopefully solving it with a fresh 2.0 motor soon--still gets ~35 MPG tho)

You need another 7ccs to get down to ~8.6:1.

Sadly the cheap Bus pistons are 15ccs, and would drop your compression too low. (~7.5:1@1mm deck)

The AA T1 94s probably have enough meat to dish like you need, but I doubt the stock ones can get you there, and have a pin size issue...(22mm, must rebush rod small end)

Your fan air intake IS fully sealed up, right?
That will kill.

Off the wall:
I have been torturing Jake lately with cam requirements, I want to "go Miller Cycle"..
The V8 crowd have been using late intake valve closing for years (as late as 70 ABDC) and running 11:1+ CRs, using the same technique, just not advertized as such, cam grinding is "magic" after all... Note that I have NO idea if that would work in an IR setup, probabkly requires a plenum due to the ~30% of the intake charge being blown back out the chamber on the compression stroke. (drops dynamic CR bigtime)

Makes for a wide power band and a more efficient motor, at the expense of some peak power.

[farmer]

Heads are 47 cc. I have a 4 cc dish in the Euro 914 pistons.
I´m also considering a swap to US 914 pistons, if I can find a good set. They have 7 cc dish, and would help a lot in the right direction.
I will tear it apart tomorrow and see what I can come up with.
T

[Piledriver]

Before you rip it apart, talk to Wally.

He's running a Web 86 in his bug, (admittedly with an EMS) and making excellent power with 9:1 CR
(He is also running 914 2.0 heads...)

Ask him for his ignition map specs.

http://www.shoptalkforums.com/viewtopic ... c&start=15

[Steve Arndt]

, I want to "go Miller Cycle"..

http://www.sturmanindustries.com/
check out the videos of on the fly otto -> miller cycle switching in real time.

[Piledriver]

, I want to "go Miller Cycle"..

http://www.sturmanindustries.com/
check out the videos of on the fly otto -> miller cycle switching in real time.

I haven't had my coffee yet, couldn't find the video, but looks slick otherwise.

[Steve Arndt]

, I want to "go Miller Cycle"..

http://www.sturmanindustries.com/
check out the videos of on the fly otto -> miller cycle switching in real time.

I haven't had my coffee yet, couldn't find the video, but looks slick otherwise.

http://www.sturmanindustries.com/main/h ... uation.htm#
click the "video" link to the right.
or maybe this:
http://www.sturmanindustries.com/images ... uation.swf

[Piledriver]

Absolutely Slick.
Imagine the cam profile completely changing to suit , in real time, depending on load...
(Tied in with a ion sense ignition, also changing timing in real time)

That not only enables Miller Cycle, but valve based throttling, which is worth ~10% efficiency, much like the BMW system used on the 316Ti---greatly reduces pumping losses.

(10% efficiency improvement is HUGE... We're talking carnot cycle efficience, so +10% moves a gas engine from ~25-30% to 40%---)

I'll be surprised if every new car/truck in 10 years DIDN'T have this setup. HUGE saving$$$, even exceeds direct injection.(which is perfectly compatible)

[bottomend]

Wow! the future! Very cool indeed....

[Steve Arndt]

I thought you would find that link interesting. Pantera EFI Lance posted that link at efi101 a few weeks ago. The Sturman facilities look nice enough to get me to move to Colorado!

This topic is perfect as today I'm back to school for the new semester. First on the plate this morning, Thermo II.

Steve

[blue thunder]

Check Wally's dynorun on:

http://www.keversite.nl/forum/viewtopic.php?t=12548

Not bad for such a mild setup....

Cheers,

Robin