Hi Everyone, Does anyone have any ideas what the ultimate ignition curve should look like for a Euro 308 with stock carbs cams etc..? I want to load it into my ECU to see if the performance gets better. The standard curve is way off for a Ferrari, so I loaded the one below, runs great but I feel there could be more. This curve assumes the static is 10 degrees The picture on the right with the progresive curve ending at 22 degrees is the standard OEM (curve1). The ECU adds the static 10 degrees to the value in the curve Image Unavailable, Please Login Image Unavailable, Please Login
I was just poking around on gerritv's site, www.dino308gt4.com, and I noticed that under the "Downloads" section, there is an article bike Mike Florio on distributor alignment. There were a couple graphs of advance curves - maybe they'll be of some help to you. It's all Greek to me, though.
be aware that the early cars use different cams and cam timing. USA spec and 78-79 wet sump cars have less agressive cam profiles and overlap.
Hi The 'ultimate' curve is in the shop manual (also on my site) and I think also in the owners manual (from Ferrari Owners site). I recall it ends at 34 degrees advance. Gerrit
The ultimate curve is not in the shop manual because the distributor timing with its springs, weights, and vacuum can never come close to what a crank triggered programmable ECU can do. The only way you will get that ultimate curve is on a dyno/rolling road. Like this http://www.sdsefi.com/techdynojet.htm You might try posting here http://www.efi101.com/forum/
Hi Gerrit The "factory" curve is a compromise based on 30 year old mechanical technology. It was OK for the period but the limits of what can be done with a set of springs and weights can never equal the programmable ECUs capabilities. You can bet if the technology existed when the GT4 was being made it would have been used! Modern fuels and ignition systems require different tuning aspects. If you load the ECU with the factory curve it runs like a dog and low revs, however increase the advance at 1800 - 2000 and you can hear the engine coming alive. The system I have allows you to use two different curves and switch between them whilst driving. Theoretically you can have one for track and one for road, or one for economy and one for sport mode. The factory curve gives around 21 mpg over a 250 mile journey which isn't bad, but the compromise there is it isn't fast. I would love to be able to switch between that type of economy and a mega nutter mode which burns 10 mpg and delivers blistering performance. Below is the latest curve I am running. It is based on the factory manual and what sounds good when you tweak the software. Image Unavailable, Please Login
Your curve look very similar to what I'm running on my QV, but my total timing is 32 degrees (4v like less than the 2v). I'd have to pull up the maps, but I'm pretty sure it's 15 at 1000, and full advance by 3000 (it might be 3500?). Of course then I pull it back down as boost goes up, which points out the part your missing, the vacuum part. Under vacuum, the 2v timing goes to something like 40 or 45 degrees, allowing improved fuel milage. If your ignition does not has a manifold pressure sensing capability, then in at least that way it's not as good as OEM GT4 technology.
In the three timing advance graphs posted they begin to retard timing after first allowing it to advance? Why would you want it to begin retarding at 4K rpm while your asking the motor to rev ever higher? Someone please explain.
Thanks, I would love to see your setup! The UK GT4 does not have a vacuum advance therefore all the curve had to come from the distributor. I have just set it up acurately at 4200 rpm at 34 degrees, but I still feel there could be more? Do you still run a vacuum advance?
Here is the start of a technical database for the F106 engine family compiled by me, Rick Lindsay and Ric Rainbolt. In it you will find the cam specs and timing along with the US numbers. Please remember that this is a work-in-progress so please share any additions, revisions or correction. Image Unavailable, Please Login
I have updated it with data from the UK GT4 owners manual. The only difference as far as I can see is the timing. Image Unavailable, Please Login
There was a post or two in the old archives recommending the instalation of a limiting ring on the advance weights. This allowed about an additional 10 degrees of initial advance and limited the total advance to 32-34. It was supposed to really wake up the engine at lower-mid revs. I believe the author stated that the curve was similar to the carbed boxers. Has anyone got that post? Off to work. chris
Strong point. Modern timing maps are at least 3 dimensional, the axis are: MAP, RPM, Advance degrees. The injected cars have 3D curves, take a look at the curves in the OMs. Ferrari doesn't draw them in 3D, just a set of curves labled with the different MAP points on the std 2D Advance Degrees vs RPM format.
Is that a good idea to stop advance movement and flat-line it at high RPM? When running my distributor on my distributor testing machine, advance still increases after passing the 35 degree @ 5000RPM mark (does not flatten out, continues to rise at a steady rate). This is after I worked on it, swapping and shimming springs and repairing the pins. Car runs smooth and strong up to and beyond 7000RPM. The tech at the dyno shop today suggested early advance will help to produce more power. The low-ish compression specs (8.8:1) of our engines can support early advance rates. I suppose there's truth to this, anybody else can confirm?
Hi Peter This is what I want to know and why I started this thread. the curve below is supplied by Black Stallion the makers of my GT4's ignition system. It delivers great economy (21mpg) but it isn't quick. I know lots of 308 owners have upgraded their ignition systems so it would be interesting to see how their curves differ. BTW the curve below on a dyno also adds another 15 bhp - so I am told.. Image Unavailable, Please Login
The curve you post should add atleast 15 hp....it used in conjunction with a turbo or blower. It looks like about 27 degrees of timing coming in VERY late. The stock timing curves already come in too late, you should be at full timing by 3500, 3000 would be better. I run something like 25 degrees at 1500.
You might want to get it on a dyno. The engine will run good with too much timing, but it will be losing hp. The 4v likes 32-34, I'd guess a 2v would want a little more, 36ish. But generally engines like the timing to retard a degree or 2 above the torque peak...if this engine like more timing up top, it would be the first one I've ever run into. Now, if it's a CIS ending, which is basically is a vacuum condition even at WOT due to restriction in the FI system, it might want extra time up top, I've never messed with one though.
You're missing the F106A for the early US GTB engine (1975-1977). It looks to be the same as the F106AB but with 240 BHP and slightly different cam timing and carbs. The Compression Ratio is 8.8:1 (I think the 106AB is 9.??:1, not 8.8). Advance is -3°+/- 2° at Static 16.5°+/- 2° at 3000RPM 34°+/- 2° at 5000RPM Carbs are Weber 46/46/47/48 E-tube F36 Main 135 Air 220 Idle 55 Air Correctors 170 Valve Timing Inlet Opens 34° BTDC Inlet Closes 46° ABDC Duration 260° Exhaust Opens 36°BBDC Exhaust Closes 38° ATDC Valve Clearances are the same Cold Idle is 3000RPM Hot is 1000RPM This is all from my owners manual.
Thank you Sean! I have revised the spreadsheet to include your data and rearranged some columns. Again, this is a work-in-progress so to all those interested, please share your knowledge for our mutual benefit! rick / '79 308GTB Standard specification Image Unavailable, Please Login
Hi Rick Just to complicate (or is it complete?) the 308GT4 distributor section, Euros came with 1 or 2 distributors (it was not just a split between US and Euro) The 2 distro Euro GT4's had DCNF's 35-36-37-38. the single had 57-58-59-60. Some jets were same between the 2, others different. Intake timing also differed: 1 D, intake open 34 btdc, close 46 abdc, exhaust open 36 bbdc, close 38 atdc 2 D, intake open 30 btdc, close 50 abdc, exhaust open 36 bbdc, close 28 atdc 1 D cold idle 2000 +/- 200 rpm (temp < 65C/150F), hot idle 1000 +/- 100 2D static advance, 6 on R2, 16 on R1 2D 3400 RPM, 34 on R1 1D static advance, 6 1D 3000 RPM, 33 From 1976 Euro 308GT4 Owners manual. Gerrit
Thanks Gang. The spreadsheet is growing in complexity and potential value. I have incorporated all the latest information. Thank you. I will post the updated version a little later. Right now I don't want to confuse the issue with more incomplete versions. Regards and thanks, rick / '79 308GTB #28133 Standard Spec. originally delivered to Germany
