1969 2.0 S high compression motor - need more mid range

[Alex Webster]

Hi all,

Seeking some information, guidance, feedback regarding a new motor that is now in my 2.0 race car.

As some background, the core of the engine was carried over from my 67S race car (now retired) and ran 40 IDS Webers. In changing to the 69E as the new race car, our local racing category rules required the induction to be changed MFI. The heads were drilled to accept the injectors, and the other necessary changes made.

We sent the MFI pump to Germany to be fully rebuilt to S spec (including space cam), we removed the 906 cams that were engine for the Webers and replaced them with S cams (as the top end was leaning out due to the long duration and lift of the 906 cams). We also installed high compression pistons (906) to take it up 10.5:1 from the standard S pistons. It runs a lightweight flywheel, single plug ignition, SSI's and a local 'Cairns' exhaust. We run a short ratio 901 box, with an LSD.

In all the engine performs well without being crazy, however the most noticeable difference is the mid range torque of the motor with the MFI.

So..... How is the best way to get some more mid range? Essentially I am not chasing more hp, but I am chasing torque, as it is the initial transition from the exit of the corner

Initial plan was to look at the tuning again, and see if we can improve the mixtures in the mid range, however am also considering the black art of headers and exhaust combinations as way to improve the torque.

Hopefully I have outlined the spec of the motor adequately, and maybe some of you might have chased similar solutions.

Thanks!

[Frank Beck]

Alex,

Please include references to RPM so we all know exactly what you mean by mid range.

Just guessing that your solution is not going to be about mid range torque but traction and gearing.

[jeff eelkema]

Hi Alex

The system by Duel in the Netherlands seems to be the exhaust of choice for FIA guys in Europe and claims to boost midrange but not cheap. They use 3 long equal length primaries linking into 2 fairly long equal secondaries before going through a longish straight muffler. The design should in theory improve scavenging which should help across the range. There are a couple of photos in an ad for Historika in the UK in the July issue of GT Porsche. I had some email correspondence with Duel a few years ago which I thought indicated they had developed a system ideally suited to 2L cars and kept within noise limits on tracks in Europe.

cheers

[jeff eelkema]

Forgot this http://www.duel.nl/specializations

[911r67]

use Solex cams...they produce more torque than the S cams.... without loosing much horsepower!

[sithot]

Forgot this http://www.duel.nl/specializations

+35% out of an exhaust? Did the other examples have potatoes rammed in them?

[Frank Beck]

Me thinks this thread will be entertaining and chock full of hyperbole and underachieving opinions.

Whenever I hear the words "I need more ..." from a racer my first question is "Do you really?"
In the case of needing "more mid range" to come off the corner better there are so many other factors involved that one has to question whether the "need" is valid. Here's a question: "Do you want to exit the corner faster or get your lap times lower?"

Sorry, I digress.

Again, RPM references will keep this conversation meaningful and honest. Specify in detail what gear and what RPM you're at in a given corner, with actual data acquisition info if possible.

[Alex Webster]

Hi guys,

Okay some further background....

In the previous set up (being the SWB 67, Weber Carbs and 906 cams), the car and I were front running. Won races outright, still hold some lap records for the class etc. For example, the track we were at last round, I was around 4 seconds off my best time in the old car and the old induction.

Laptimes for that track are around 1m 40 seconds. I was in the 1m 45's.

So without trying to sound full of myself, I am considered to be in the front running drivers for our category, but was stuck mid pack (even on a clear track) and unable to get much beyond that.

Upon reflection, the term more torque is probably better explained as a flat spot whereby the car almost feels like a 3.0 Turbo (the flat spot part!).

Other things that I have considered in the rationale behind the lack of speed are, new car being LWB(old was SWB), MFI (old was Carbs, and LHD (old was RHD) but this should make it quicker, or at the very least around the same.

Harvey to your point/question - the cams in the old set up were 906 and we have brought them back to 'S', the ports were standard heads that have smaller exhaust valves to try and keep some torque in the motor, but the inlets increased. With that, removing the flat spot rather than more torque, might be an more adequate explanation. I am used to have a relatively low hp car and battling against the V8's and carrying high mid corner speed. That is what having a2.0 litre is all about

I agree with the comments raised as you have Frank - do you really need it?! I would be the first to say 'learn to drive first', then chase more power etc. I have done that with friends cars who say they need for hp or displacement. I jump in their car, knock 3-4 seconds off their time, and throw them back the keys and say 'try again'.
I think I can drive (but no pro), and I think I can get pretty close to the capabilities of the car (especially a 356 or early 911) pretty quickly irrespective of the engine, suspension setup etc.

Rev range is peak Hp around 7200rpm so it revs to around 7500rpm. As for where the car really feel flat, it is from around the 4000rpm to around 5000rpm. From there it spins out well all the way through to 7500rpm.

I need to pull the data telemetry (VBox), however the gears it felt the worst in (given the track we were at) was in 3rd gear in that range around 4k-5k. My in car cameras decided not to work all weekend, so I don't have footage either! DAMN IT!

Frank you are right "Do you want to exit the corner faster or get your lap times lower?" Yes I want to get out of the corners faster, as the point where I am ready to get on the gas. That in turns gets you high top speed, and lowers your lap time in the process. Especially getting out of the slower corners quickly is the key to fast lap time. Don't need to tell you that!

Hopefully that helps.

[BOYER73S]

Who built the engine...thats probably the nut of the problem Alex.

[edmayo]

I think a good start would be to see what the fuel curve is, especially in the flat spot range.