Tuning an EFI

[Roy]

Okay, we have gone into pros and cons of EFI on the carbruettor topic so propose we start afresh

Looking at Simon's post: "Roy,Have a look at this little lot. It might wake up your EFI system - S&S Cycle - Performance Parts for American V-Twins" - I am interested in getting my EFI a bit more responsive but must admit; I have not a clue to what bits I should consider and what improvement they may bring. Has anyone tuned a EFI - the 52mm EFI body looks like a good starting place... ??? Would I need to get my PCIII retuned??? Would it be better to start with an Andrews 21 Cam 1st??

Help!

Cheers, Roy

[Scotty]

Shit, if this takes of it should be a fun read, there are about a trillion different tuning systems (and opinions) for these things!
(google "Harley EFI Tuners" and you'll see where I'm coming from)

I've been looking into EFI for quite a while now, and no one seems to agree what is the best tunner or the best way to tune them!

Good luck with this..

[Roger]

An add-on tuner can never be effective as a tunable EFI unit. If you're looking at the S&S injectors, look too at the S&S EFI unit. Not an add-on it's a fully programmable closed-loop system

[the_monster]

With any tuning, it is always best to know what you want to get the bike to do at the end of the day - as it can an expensive question of trade offs between grunt, top speed, economy, stopping and stability. The deeper you go the more expensive it gets.

[Mike Benis]

And if you do a fair bit of touring, don't forget that the closer you are to stock the easier it will be to fix....

[grbrown]

Originally Posted by Scotty

I've been looking into EFI for quite a while now, and no one seems to agree what is the best tuner or the best way to tune them!

Good luck with this..

Scotty,

In actual fact that is the case with any tuning mods for any model of Harley! There is such a wide variety of options available, especially for Evos and TCs, plus umpteen specialist dealers to mix and match them, that there is no single answer to any tuning question.

On the original question, tuning of a Harley involves undoing the emissions related harm done to them, which could sensibly include replacement cams, revised ignition timing, improved EFI air/fuel ratio mapping, improved intake breathing and ditto exhaust. Don't forget also that overall gearing is way over the top and can beneficially be reduced to improve performance, especially on standard/mildly modified bikes.

[Scotty]

Choices..

Thundermax, Sert, Harley race tunner, Daytona Twinteck, TTS Mastertune, Remus, S&S VFI, XIED's, Headquarters Pro tuner, Power Commander, to name but a few, and believe me the list goes on.
You can go from having a flash installed in you ECU from your local dealer to completely replacing your ECU, and everything in between, its a bit of a mine field and every one has there own idea of which one is best.

A couple of things to read.

Harley-Davidson Motorcycle Fuel Injection Explained

Harley-Davidson Fuel Injection Upgrades

[Roy]

Originally Posted by grbrown

Scotty,

In actual fact that is the case with any tuning mods for any model of Harley! There is such a wide variety of options available, especially for Evos and TCs, plus umpteen specialist dealers to mix and match them, that there is no single answer to any tuning question.

On the original question, tuning of a Harley involves undoing the emissions related harm done to them, which could sensibly include replacement cams, revised ignition timing, improved EFI air/fuel ratio mapping, improved intake breathing and ditto exhaust. Don't forget also that overall gearing is way over the top and can beneficially be reduced to improve performance, especially on standard/mildly modified bikes.

Graham, one of the things I am looking for is a sensible set of steps to improving the overall cruising speed of my streetbob. When I go over to Europe, I like to 'cruise' .. erm .. quickly ... and dont want to feel like I am taxing the engine too much. Recently I had a 34T front [rear belt drive] pulley fitted which has made a real difference, so really want to identify what my next step should be - I have a PCIII (professionally tuned), S&S (with a K&N element) and bigshots (with 'quiet baffles'). To try and maintain some kind of sensible mpg while increasing my cruising speed, looking for suggestions on a next sensible mod - cams?? learn to drive slower .. nah, lets keep with realistically achievable stuff

So, is it cams, bigger EFI body, closed loop system that Roger mentioned, I don't really understand what each of these changes would make. Can anyone help spell it out to a mechanical thicky?

Cheers, Roy

[Monkeybrain]

Cams and closed loop.



The tuners and even the SERT to some extent don't adjust on the fly, if you don't mind the o2 sensors and the wiring for them, invest in a closed loop system.

As for cams, well thats another 'cam' of worms........

[grbrown]

Roy,

On gearing, I have fitted a 21T crank sprocket in place of the original 25T on my Dyna. That reduces its theoretical top speed from 140mph to 118, in other words to about 19mph per 1,000rpm. The only other mods are a jet kit (it has a carb), SE air filter and SuperTrapp mufflers. Roll on in top gear is now like a Harley should ride and gear-changing is significantly reduced. However that is contrary to the mis-guided popular belief that Harleys should lug monstrously tall gearing, hence never get going!

I don't know what the performance figures of my Dyna are, but I have had the S&S 107 in my Glide dynoed. Between around 2,700 to 5,500 it gives 90 to just over 100 ft lbs of torque. With top gearing of around 24mph per 1,000rpm, fast touring on the Continent, just a couple of weeks ago, involved travelling at between 3-4k rpm, in the sweet spot of that plateau of torque. Is that what you are after?!

Returning to your bike, if you have raised your gearing, without substantially increasing torque to compensate, I question the benefits. I have over 100bhp to back up my 24mph per 1,000rpm! I suggest around 4k rpm at 90mph for a sensible top gear for Continental cruising, unless you have similar bhp and torque figures to my S&S.

So one suggestion is that you get your bike dynoed in its present form, to see what you currently have. The scope to build upon that is substantial, whatever the numbers! In the extreme you can bore and/or stroke your motor, raise compression, gas-flow the heads, plus all the other things we have already mentioned.

A few years ago I had my original evo motor stroked and tuned by a reputable builder (now retired unfortunately) and it ran as sweet as a nut. The more you research this topic on the internet and seek advice from us rank amateurs, the more, not fewer, answers you will get! At present you are onto a hiding for nothing.

It sounds as if you have serious ambitions for your bike, as I had when stroking mine and recently installing my S&S. There is in my view only one worthwhile solution, namely find yourself a reputable engine builder, discuss your requirements in detail and evaluate if he understands and can supply what you want. Don't presume to tell him what to fit or how to achieve the results you want, that is for him to judge - that is the reason for going there. Then get him to build it for you! You cannot achieve comparable results yourself without substantial experience and expertise. If he is worth his salt, he should make it all seem very easy and you will marvel at the final result, believe me!