The S&S IST Ignition

[David Jackson]

Hi Mike;

Previously you mentioned the high price of the IST unit; close to $700. You also mentioned that various HD units are pretty good and pretty close. (I have the one which allows curve and advance choices.) However, the S&S unit is the only one which "learns" what max spark lead is previous to detonation and so theoretically always has the most advanced timing possible, under all operating conditions. Do I understand it correctly this far?

Then it seems as though it is the "answer to a maiden's (or a Harley nut's) prayer" because you never have to worry about ignition timing again; you never have to worry about dynoing for max ignition performance and all that. It sounds too good to be true!

However, usually when something sounds too good to be true it is.... so next question; assuming the IST ignition keeps the advance at the max ... Is Max Advance something we always want, or are there situations during which some retard of the timing will provide better performance? I do remember my VL having advance on the left handgrip for retarding during starting and also for going up hills (no, I am not old enough to have bought it new!).

Can you enlighten me on this?

Thanks;

David Jackson

[Mike]

You are correct. Current thinking is that we want as much advance as the motor will allow at all times. I think S&S is really on to something with the IST ignition ( I'm somewhat surprised that H-D has not done something similar-it may be a durability issue or testing of same). Because of the extremely poor combustion chambers, heat retention and lack of cooling oil, iron head XL's, VL's and Fl's required the timing to be really retarded to prevent detonation yet had to be really advanced (up to 45 deg) to make power. The amount of advance is a relative thing, it's all about the burn. A lot of advance in a TC motor is 35 deg and as stated earlier the amount of required advance is an indicator of a motors effeciancy (import motors routinely run 22-25 deg adv.). The only open question with the IST is it's long run durability and accuracy. We do not know, at this time, how long lived the accuracy of the knock sensor is. Since the system lives and dies by this sensor, this is a critical question and is one reason why similar systems have not found their way onto O.E.M.'s which MUST live for 200,000+ miles and maintain accuracy. With the milage a motorcycle normally sees, this is far less of an issue and makes them a good starting platform.
Regards, Mike

[David Jackson]

Hi Mike;

You have answered my question so I don't know why I keep going ... but you did say quite clearly that "current thinking means that we want the motor to have as much advance as it can stand at all times", or words to that effect.

Aside from a possible reliability issue and a high initial cost, what possible reason could there be for not having one of these units? If my carb comes back from Bobby Wood properly set up for my cams and so on; and the ignition does not have to be messed with, why would dyno time be even needed? Sounds great to me.

I have ordered the Fueling Cam Support Plate, with everything else I am doing is there any reason not to get the Fueling Oil Pump as well?

I think after this winter's spending orgy I want this bike to run hard for a long time! About the only weakness for this displacement at this point might be that the SE HTCC CNC ported heads and 10.5 pistons might not be a person's first choice; though they are not all that bad, I imagine.

Regards;

David Jackson

[Mike]

Definetly do the Fueling pump with the case mods that have been done. We would still recommend dyno time just to make sure the carb is optimized for the rest of the combo and to confirm your investment. With the IST there would be no ignition adjustments so dyno time would be limited. With the 408 cams the pistons and heads will be fine.
Thanks, Mike

[David Jackson]

Hi Mike;

Fueling Pump is ordered, along with the Feuling cam plate. S&S IST ign ordered. Even though a little expensive, WA 505 is happening. I have the Boarzilla. (I understand D&D is making quieter baffles for these, going to check that out. I also have a set of SE II slipons w/stock headers, and a V&H Pro Pipe in the garage. If some other exhaust system will give great power with less noise I am willing to hear about it as well. Wondering about having someone build stepped header pipes and adapting some of those big cans the imports use? Also, what about Cycle Shack one piece pipes with big diameter header pipes?) Gear drive cams & kit are here. Have brand new set of Jims good guy lifters. Stock 5 speed going back to minimize hp losses. Using stock primary chain adjuster. Case breather mods done. Have the new HD 113" slugs and jugs. Heads already have good guy HD roller rocker arms and supports in them. Planning to send flywheels to Northwest for balancing. Have heavy duty clutch spring installed and HPC clutch goodie. On BW's advice, going to 3.37 gears. I have a Sputhe hot rod motor mount adjustable system here in the box. I have the frame mount HD oil cooler already installed. Have ordered the handlebar mount oil temp guage and bracket. Am I missing anything motor wise? Besides the ideal exhaust system, of course.

And, on oils; I know HD syn is good but pretty pricey. Do you like MOBIL 1 as well as the HD syn? I have read synthetic oil keeps the temps down a little. BW suggested I keep an eye on oil temp, no more than I think he said 220 or 230 degrees. Would you think I would need the vertical oil cooler as well as the horizontal one I have now?

Thanks;

David Jackson

[Mike]

The Cycle Shacks work but those you see with dyno charts are 2'' M pipes without baffles. We run Yoshimura cannisters on our XB AMA racer with stepped head pipes. Everything sounds great!!! Design operating range for the oil is 210-250 (H-D has no problem with 280). The syns do seem to reduce temps typ. about 10 deg. I like Mobile One (so long as it is that for american v-twins) though as a dealer we recommend Syn 3. A second cooler should not be required and may cool too much. Much below 180 deg the oil is not working at it's best.

Regards, Mike

[David Jackson]

Hi Mike;

I contacted Yoshimura a year or two ago asking about any cannisters or any help they could give for a Harley. They basically seemed to think Harley Davidson motorcycles were from Mars or something, and would give me no help at all; not even any hints about cannister size or anything! How did you figure out what to use?

Regards;

David Jackson

[Mike]

The inlet and outlet size determined which to buy then we cut the things to pieces (we have two), completely gutted them, shortened them to fit our belly pan and rear section, re-oriented the oulets, cut the baffles down 1/3 to create a plenum area, repacked the glass with stainless steel wool, re-assembled and got blackflagged first time out for noise!!!!! One db over the max.! Next set will have full packing. The entire motorcycle is like this, but it does make two hp/cube (it's 1334cc/80ci).
Now you can buy one from Buell, the XBRR(which is what we named ours three years ago) for about 1/3 what we have invested in ours. Dagnabit! BTW, we're on the list for one.
Regards, Mike