need more power from my S4

I have a 2001 S4 with a open air box and Arrow slip-ons. I also went down 1 tooth on the front sprocket. I live at a altitude of @ 7,000 feet. With out getting into the motor does any one have any ideas on what my best bang for the buck should be? Any one have experance with a power commander at high evevation? Any other ideas for a cheep mod? I just dropped a load of cash on new rotors so I'm a little tight on money. Any help would be great.

Mike

go up two teeth on the rear sprocket for a 14/39 final drive ratio. very good results here. very short money because you should still be able to run your stock chain. it'll just take adjusting the rear wheel all the way forward in the swingarm adjustment range.

later... the only real mod i can think of is SPS cams and either a full silmotor (or termignoni) system or a custom system based off an ST4 header (45mm instead of 40).
but thats BIG coin....

thanks s4strati,
I'll get a sprocket on order today. Any idea if a power commander would help? or and other mods to the fuel and timing?

The Powercommander will help. If you do the full exhaust and cams it's a must. The next step beyond cams would be high comp pistons and head porting/engine blueprinting. Now your talking real big$$$$. Frankly, with cams,exhaust and custom PCIII, the bike runs like a banshee. If you need more hp get a 999.

turbo, nitrous, supercharger, etc... time to think outside of the box.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s4strati &raquo;</TD></TR><TR><TD CLASS="quote">go up two teeth on the rear sprocket for a 14/39 final drive ratio. very good results here. very short money because you should still be able to run your stock chain. it'll just take adjusting the rear wheel all the way forward in the swingarm adjustment range.</TD></TR></TABLE>

Strati, the S4 has a 15 tooth countersprocket (OEM configuration is 15/37). 15/39 is perfect for me. Stock chain fits, no problem (although I've since changed to a longer chain). 14/39 would be a bit too much imo.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by infoage1 &raquo;</TD></TR><TR><TD CLASS="quote">Strati, the S4 has a 15 tooth countersprocket (OEM configuration is 15/37). 15/39 is perfect for me. Stock chain fits, no problem (although I've since changed to a longer chain). 14/39 would be a bit too much imo. </TD></TR></TABLE>
i recommended going to the 39 out back because knapp mentioned he already went down a tooth in front. your bike running 15/39 is very different than a mostly stock s4 running 15/39. you've got them fancy red-heads, don't you?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s4strati &raquo;</TD></TR><TR><TD CLASS="quote">i recommended going to the 39 out back because knapp mentioned he already went down a tooth in front. your bike running 15/39 is very different than a mostly stock s4 running 15/39. you've got them fancy red-heads, don't you?</TD></TR></TABLE>

Sorry, I missed the previous mention of that knapp717 had already dropped a front tooth. His current combo is not much different then mine. No red-heads (that's foggy123), but not stock heads either .

Mike, I have a PCIII and I regularly ride from sea-level to 7000+ feet. Runs fine all the way up and back. No issues at all.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by infoage1 &raquo;</TD></TR><TR><TD CLASS="quote">Sorry, I missed the previous mention of that knapp717 had already dropped a front tooth. His current combo is not much different then mine. No red-heads (that's foggy123), but not stock heads either .

Mike, I have a PCIII and I regularly ride from sea-level to 7000+ feet. Runs fine all the way up and back. No issues at all. </TD></TR></TABLE>
that's right... you bolted on those hotted up 916 heads, right?
my bad.
i still vote for 14/39. if you're not spending a lot of time at 90+ mph (long stretches on highway), i think it's a great ratio for the s4.

got a 39 tooth today. Won't have time to put it on till friday. I'll let you know what it's like.
I know I was asking about cheep mods, but does anybody have feed back on a big bore kit or if you can bolt a 996 cylinder and high comp pistons?

thanks
Mike

I think the 39 tooth in the rear is a great improvement. Great bang for the buck. It was only 54.99 and it is lighter than my stock one (aluminum). My new rotors should be here today. Pretty excited about the weekend.
On a side note I also helped a freind with a new tuono put a full Akropovic system and new SBK replica eprom. Holy crap!!! If only my bike would ever run like that. I'm not going to ride his bike anymore. Makes me jealous. Bastard!!!

The main problem for you is high elevation and that gives lower air density and air pressure, lower combustion chambre pressure and due to that a big power loss.

At 7000ft the air pressure is 25% lower and the density is also 25% lower. That results it that your very nice 916cc engine with 11:5 compression will work like 690cc engine with much lower comperssion. If it is 11,5:1 original it will be approx the same as 8,6:1 in compression if I did not calculate it wrong. On top of this it might run very rich if the ECU does not have a correct pressure compensator.

That can only be solved by more cc and higher compression and a maybe a proper ECU.

If you want more power but do not want to compensate for the air density/pressure the first step i would suggest on a S4 is to fit different headers. All 916:s exept for S4 has 45mm headers. The S4 has 40mm.The cheapest way is to find some used ST4 headers and slipons and modify. If you keep your eyes on ebay the ST4 systems comes up now and then. If you do this you will need a power commander and a custom map. I bought my ST4 headers and ST4 silmoto aluminium slipons for 300 Euros at Ebay. I guess that is 400 dollars. Add 300 dollars for a Power Commander and you will need a custm map on top.

This works very nice at low altitude. It might have less effect at high altitude. I dont know.

The next step is to look at ebay for 996 SPS cams. They will make a big difference but it will cost a bit more. I payed 500 Euros for my cams.

I just started the road mapping on my S4 and it has following mods.
ST4 headers, sil moto ST4 slipons, SPS cams timed to 107/107, lightened flywheel and a PC3 USB and it is a big improvment. The plan (dream) for the future is a ST4S or a MS4R engine with 68mm stroke and HC pistons with SPS cams but I guess it will never happen.

Jocke..........

Modified by vij at 12:20 PM 5/14/2005


Modified by vij at 12:22 PM 5/14/2005


Modified by vij at 12:23 PM 5/14/2005

got the rotors on. They are not broken in yet. I hope they get alot better. Not much bite and you have to use alot of pressure. They are Galfer Wave Rotors with new Galfer pads. Any one have experance with them? I did not have a chance to put many miles on them and am hopeing for a lot of improvement.

Mike

You might also want to look at lightening some parts, mainly the flywheel and clutch. Won't give you anymore power per say, but it will get you into your powerband quicker. I have had a nichols flywheel on my S4 for a couple of months and I'm happy with it. I only rode the bike a few times before I swapped the flywheel for the lighter one, so I really don't remember how it rode with the stock one. I threw a yoyodyne lightweight clutch kit on last night and I'm also very happy with it. Much quieter than the stock setup and tons lighter. Very impressed. It seems like the clutch kit had more effect than the flywheel did. Which probably should be the case since I think the stock clutch setup weighs more than the stock flywheel. Flywheel was around $200 (+ $50 for the jamnuts) and the clutch kit was $600 (+ $150 for barnet alum. plates).