Timing

[zigzzagz]

From some reading I was doing at RBRacing site, aparently setting timing is a much more difficult thing to get right than even fuel mapping. Also read that on a big motor like my 124" tuning and timing together being slightly off can mean 10 or so HP. I'm just wanting to cover all the bases before trying out other parts. It's one of the things I am wanting to look into in my apparently lacking power. I'm trying to find some maps from other 124" twin cam owners who have had more succesfull tunings and that have achieved better numbers than myself. So Im wondering what I should be looking for in this map, and what I would be able to use. Should they have the same kind of compression and cam as myself? Or would most motors of this size have similar timing needs? Would a 124" have different timing than a 116" or could a 116" ign. map be used? Some of the people I've spoken to have asked if when the bike was tuned if 'full timing swings' were done, and I don't have a clue what they mean by that. Also does the SERT have a timing map that is seperate from the fuel map, or are they one in the same. Just wondering if I can plug in someone elses timing map and not have it affect my fuel mapping. I'm the only fuelie this large come out of the shop so I'm sort of bound to look around a bit myself as I'm the ground breaker.

[Mike]

Timing can be affected by so many things it almost does come down to an individual motor thing. 2-1 exh vs staggered duals can affect the timing needs of a motor. Cylinder pressure is typically the most influential when all other things are equal. Different head chamber/piston designs (HTCC vs Bathtub) will have large affects. And a bunch of other things too numerous to list! For all the above reasons, some bikes do not respond to timing changes well. You can make large swings in timing and see very little affect while on others you'll see changes with as little as 2 deg differences. Bikes which respond to small timing changes are a sign of more effeciant motors, as are those that want very little overall timing (I.E. 28deg vs 36deg). Timing swings I would interpret as making timing adjustments then a dyno run to see the affect. I.E., retard the timing in 2deg increments per run until power or torque drops off then go the other direction by adding 2deg increments/run, from base timing, again until power/torque drops then selecting that which gave the best results. This would be for WOT only and the rest of the mapping would have to be done under varying load, TP's, MAP, temps. and rpm. This is very time consuming and few are willing to pay for the dyno time. So we end up picking and choosing certain test/tune areas then blending around them based on experiance and/or complaint.
SERT treats the timing "spark" tables seperate from the fuel "VE" tables and has a table for each cylinder. Yes, you can import tables from other files. This is one of the great features of SERT, just save each file seperately so you can always return to the others or the base file.
Regards, MIke

[zigzzagz]

Had the bike retuned and picked up another 7HP I'm happy to say. Required them to lean out to 13.5 - 14 in upper rpm at wide open throttle. Hope this doesnt result in a bunch more heat. Last summer I was seeing temps of 240 - 250 but only in bad traffic, with a usuall 220 temps highway cruising. Although that was with dyno oil and I did just switch to synth which may help. Say, that brings up a thought. Is it possible that the swap to synth could be responsible for part of the gain? I have heard it reduces friction quite a bit better than organic oils. Anyways. wherever the HP came from I'm happy for and can rest now...... well, for a bit anyways. Sure do like those new billet heads I saw on the Revolution performance page. I guess I'll have to see how they work for Dave in Las Vegas NV first. Lol

[zigzzagz]

One other thing does come to mind Mike. With these boarzilla pipes. I do know of one person who swapped out the zilla for a basanni road rage. He lost a few HP, 3 or 4 but picke up 10 lbs/ft of TQ. Is this common? The boarzilla more a top end HP pipe? I would expect the road rage is a 1 3/4 pipe whereas the zilla is 1 7/8 stepped to 2" and it may be the higher velocity of the RR that is getting him the torque. What other pipes do you like for the big big inch bikes? I do know there is the lightning header, and RB Racing but can't think of any other specific pipes for big motors. Ultimately is a fabbed exhaust built to the motor the way to go? Also I'm going to try to stick in one more question here. Is it possible to do any intake tuning with these fuel injecteds? I know/ or have read that if you could get independant runners of about 12.5 inches attached to a plenum of 40 - 60% of CID and then your carb you could find 15 - 20 HP if the exhaust is also tuned. Is this the same for injecteds? Obviously that is alot of gear under your right leg, but surely there must be some way to get the benefit of tuned intake with your manifold/throttle body?

[zigzzagz]

Mike. There's an absolutely beautiful dyno on Bob Woods website, of a 120" with Baisley heads and TW9b cam Latus 52mm throttle body and boarzilla making 149HP and 144 lbs/ft TQ. Man, what a beauty of a run! HP keeps on keeping on right up to 6000 rpm which seems to be quite unusual for a big motor like that. It's just where I'm wanting to be with my 124". I notice the larger the stroke the earlier in the rpms the power starts to sign off. Is there any way to combat this? As obviously keeping your torque hanging on longer will amount to bigger HP numbers as well. Also, do you have any idea what the static cr. would be in this build? One other thing I would like to ask. I know in the case of carb'd bikes, sometimes adding a spacer between the carb and manifold will sometimes make quite a big difference. Is this the same case with injecteds?

[zigzzagz]

Wow. more amazing yet, I went to get the link for posting here and it's only a 117". That's a 4 3/8 stroke I think. Are those baisley pro-street heads from stock castings? Are his hybrid heads? Man, this dyno just gets me all worked up. Lol
117" latus dyno. Sweet!!
http://www.woodcarbs.com/images/tc117efitw9bg.jpg

[Mike]

Have not run the Revolution heads to date. Oil temps of 240-250 would be normal for traffic conditions, no worry's! 13.5-14.0 seems lean but if it makes more power then that's what we're after. We do not want to sacrifice performance for perfect fuel curves. The Boarzilla's and RoadRage's perform similar in 95ci motors but the RR seems to be morre sensitive as the motor size goes up. Also the RR for Softails is not stepped and does not perform as well as the touring version. Our Exhaust test and compare dyno library is not complete as yet but we have several direct comparisons of these two pipes. So far the D&D's have been the overall best. Not much data on the RB's also but what we do have suggests they too may not like big motors. A fabbed system would allow concentration of the power curves but would give up elsewhere, typ. down low.
Intake lenght tuning is mostly a physical problem with H-D's but S&S has attempted this with their VFI Tuned system. 12-14 inches is considered the ideal for an H-D but is a fuunction of which pulse and RPM we are tuning for. Rule of thumb is the higher the RPM the shorter the lenght. Exhaust also effects this and the two should be tuned as one. Unresolved questions at this time are throttleplate placement, total volume and tapper rate among others, at least from a practical standpoint. To be effective the runners should be independant but now realistate problems occure.
The 117 uses Baisley Hybrid heads with Axtell pistons set to 10.7 compression and a D&D Fatcat system (it was a prototype and we thought at the time it was a Boarzilla). The bike is back for more chrome and we're going to the Boarzilla with a new tune but it now has a 6speed and this may cancel any gains on the dyno. The owner lives in South Carolina and ships the bike to us for motor work and tuning so it's quite an undertaking.
Apologies for the delay in responding, hope to be able to stay on top of reply's as we can.
Regards, Mike