EFI Scrambler power gains

[sadsack]

Don't hit the newbie!
But I've been trying to find info here on power gains for an efi scrambler and mostly all I can see is for carb models. Anybody got any good links, mods, etc for boosting these model scramblers? I'm looking at some D&D pipes (though I can't seem to get any solid feedback on what they actually do in terms of power)... I'm in Spain, so if there's any UK/European based dealers that anyone knows about offering kits I'd be really interested...
thanks in advance/rory

 

[taw1126]

I don't have an EFI Scrambler but I thought one of the biggest issues (maybe the only issue) is getting a new computer "tune" loaded for whatever changes you make. Several of the U.S. parts dealers sell computer interfaces so you can do it yourself; having never used this I'm not recommending it...just the first one I could find:
http://www.british-customs.com/powe...riumph-bonneville-thruxton-fuel-injected.html

Otherwise, it looks like the changes (AI removal, airbox elimination, new pipes) are the same for EFI & carbs:
http://www.british-customs.com/british-customs-triumph-thruxton-efi-basic-performance-package.html

You might find more EFI performance information in the Thruxton and Bonneville threads.

 

[Aussie_T100]

The only thing stopping you making a direct comparison between a modded EFI Bonnie and a modded EFI Scrambler is that the Scrambler has "softer" cams which are designed more for low down torque than higher RPM horsepower.

Depending on your intended use for the bike you might want to consider upgrading the cams to something more performance orientated in addition to airbox removal and free flowing pipes but either way you will need to attend to fuel mapping via the uploading of a modified fuel map using a Tuneboy or similar device.

I suspect that 60 - 65HP would be possible with stock cams and possibly 65 - 70HP with cams. Those would be realistic targets at least.

 

[sadsack]

thanks for the input... i'm off to investigate the bonnie threads.

 

[Speed3Chris]

I'll weigh in to help a bit. I ride a relatively stock EFI bonnie.
There are really two areas both the bonnie and Scram are seriously deficit. Both lack compression and cam timing. 9.2:1 CR doesn't cut it when it comes to compression when pretty much all high performance bikes have 11.5 - 12.5:1 compression and all the stock cams in both bikes are weak and postured to low and mid range. Scram cams are the worse if you look at it that way but what give the 270 deg motor its great tractibility. This is by intent. A very knowledgable owner...in fact two I know with Scramblers changed the inlet cams to earlier 790 270 deg inlet cams with desired result...more hp up top...but be careful what you wish for as without more compression and greater overlap you will be left with a hole in mid range performance because dynamic compression is reduced with hotter cams. The exhaust cam across the board for both bikes is much better than the inlet cam. The 865 360 deg inlet cam on the bonnie is better than the 865cc 270 inlet cam for the Sram in terms of maximum output. You have to ask yourself how you ride the bike whether moving up the powerband is desirable....generally no free lunch. Also ignition timing matters. Best recipe for the home tuner is...1 or 2 more degrees of ignition timing, 1 pt more compression and 790 inlet cam for either the bonnie or scram if you want to wake up your stock bike. The ignition timing and compression will fill in the low and mid range you will have more power up top because greater overlap and duration.
You don't have to buy HC pistons to get another pt. of compression. Many believe that milling the head or cylinder height is taboo but it is done all the time in Europe for more performance. Some even take out the base gasket which is a technique I don't endorse but also is done across all motorcycle brands for about .3 more pts. of compression as a general rule. The bonnie and scram motors need more squish operating with almost 2mm of head to piston clearance. 0.5-0.7mm is more desirable not only in terms of more complete combustion but higher compression. Taking .040" or 1 mm off will bump compression by about 1 full pt and wake up the bike.
Some food for thought. On a budget you can hotrod these bikes as they have tremendous potential without spending a lot of money.

 

[sadsack]

Great post. Thanks for the all the info. I'm off to take a popular mechanics course now!

 

[Aussiebikerdave]

...You don't have to buy HC pistons to get another pt. of compression. Many believe that milling the head or cylinder height is taboo but it is done all the time in Europe for more performance. Some even take out the base gasket which is a technique I don't endorse but also is done across all motorcycle brands for about .3 more pts. of compression as a general rule. The bonnie and scram motors need more squish operating with almost 2mm of head to piston clearance. 0.5-0.7mm is more desirable not only in terms of more complete combustion but higher compression. Taking .040" or 1 mm off will bump compression by about 1 full pt and wake up the bike.

My experience might be of benefit here. We treated our EFI Scrambler to a port and polish, a 1mm head shave and a set of Thunderbike cams. Together with the Arrow 2:1 system and the air box removal kit we saw 72hp and 59ft/lb. Since then we have fitted a Wiseco 904 kit and associated high comp pistons without any head/piston interferance problems. Comp is now a calculated 11.6:1 and the bike although not re-dynoed, feels like it might be pulling around 80hp with torque to kill for! "Torque to kill for"? Let me explain. When in traffic, if the way is clear to overtake say a bank of three cars from 90-100kph, a top gear roll-on will have the bike acelerating like a bastard to 150-160 and building fast as your complete the overtake. In this regard, the bike is not a lot slower than my 1050 Speed Triple and Rocket 3 Touring and like both of these, is happy to poke along in town at 50kph in top. Unlike a Ducati!

 

[roadscum]

I think you'll be happy with improvements when adding a 2:1 Arrow and the appropiate Triumph tune. If you're want more then add high compression pistons and a cam along with a PCV or other tuner. If you have deep pockets well... just follow the track of Aussiebikerdave. :shh:

You'll also want to consider upgrades to the front brake and the suspension.

 

[Speed3Chris]

My experience might be of benefit here. We treated our EFI Scrambler to a port and polish, a 1mm head shave and a set of Thunderbike cams. Together with the Arrow 2:1 system and the air box removal kit we saw 72hp and 59ft/lb. Since then we have fitted a Wiseco 904 kit and associated high comp pistons without any head/piston interferance problems. Comp is now a calculated 11.6:1 and the bike although not re-dynoed, feels like it might be pulling around 80hp with torque to kill for! "Torque to kill for"? Let me explain. When in traffic, if the way is clear to overtake say a bank of three cars from 90-100kph, a top gear roll-on will have the bike acelerating like a bastard to 150-160 and building fast as your complete the overtake. In this regard, the bike is not a lot slower than my 1050 Speed Triple and Rocket 3 Touring and like both of these, is happy to poke along in town at 50kph in top. Unlike a Ducati!

Really well done Dave.
A couple of quick questions please:
- Did you mill the head or shave the cylinders 1.0mm?
- Did you clay the motor with 1.0mm shave + Weisco BB kit to determine what kind of piston/valve to head clearance/squish you had?
I know that the Weisco HC pistons do erode some of the big stock clearance to get to a more respectable 10:5 CR and you were working with 1.0mm less clearance. I believe a stock motor can tolerate 1.3mm head to piston reduction for safe clearance so am wondering how much clearance you have with calculated 11.6:1 CR + TB cams which have fractionally more lift than the 790 270 deg cams?

Thanks for any clearance information you can share and your Scrambler is very sweet.

 

[Aussiebikerdave]

Really well done Dave.
A couple of quick questions please:
- Did you mill the head or shave the cylinders 1.0mm?
- Did you clay the motor with 1.0mm shave + Weisco BB kit to determine what kind of piston/valve to head clearance/squish you had?
I know that the Weisco HC pistons do erode some of the big stock clearance to get to a more respectable 10:5 CR and you were working with 1.0mm less clearance. I believe a stock motor can tolerate 1.3mm head to piston reduction for safe clearance so am wondering how much clearance you have with calculated 11.6:1 CR + TB cams which have fractionally more lift than the 790 270 deg cams?

We milled 1mm (.0039") off the head. Didn't do any checks other than to turn the motor over carefully on reassembly to make sure nothing snagged then rode it progressivly at higher and higher revs until running it to the limiter at 8200 with no ill effects. The reason we didn't go to the extra trouble of measuring valve/piston clearances was that I was reasonably confident that we would still have enough clearance after reading as much as I could on the numerous more extensive mods that many had done before me. Dave

 

[Speed3Chris]

We milled 1mm (.0039") off the head. Didn't do any checks other than to turn the motor over carefully on reassembly to make sure nothing snagged then rode it progressivly at higher and higher revs until running it to the limiter at 8200 with no ill effects. The reason we didn't go to the extra trouble of measuring valve/piston clearances was that I was reasonably confident that we would still have enough clearance after reading as much as I could on the numerous more extensive mods that many had done before me. Dave

You are a man of good faith. Your motor has to be tight. Valves have to be tight to the pistons with reduced cylinder volume due to HC pistons + 1.0mm head height reduction. Rule of thumb is .1mm off = .1 pt CR increase. 10.5 CR of Weisco BB is mostly due to a taller piston by about 1mm. You took 1mm off the head in addition. Stock these motors don't have much more than 2.0mm clearance max. Good to know you have no interference at full rod stretch at redline.

Your bike must be a blast to ride. Love the cosmetic changes as well.
Sounds like you have a stable of nice Triumphs and thanks for sharing your hotrodding with us.

 

[sadsack]

My experience might be of benefit here. We treated our EFI Scrambler to a port and polish, a 1mm head shave and a set of Thunderbike cams. Together with the Arrow 2:1 system and the air box removal kit we saw 72hp and 59ft/lb. Since then we have fitted a Wiseco 904 kit and associated high comp pistons without any head/piston interferance problems. Comp is now a calculated 11.6:1 and the bike although not re-dynoed, feels like it might be pulling around 80hp with torque to kill for! "Torque to kill for"? Let me explain. When in traffic, if the way is clear to overtake say a bank of three cars from 90-100kph, a top gear roll-on will have the bike acelerating like a bastard to 150-160 and building fast as your complete the overtake. In this regard, the bike is not a lot slower than my 1050 Speed Triple and Rocket 3 Touring and like both of these, is happy to poke along in town at 50kph in top. Unlike a Ducati!

Can you smell the jealousy from where you are on the other side of the world?

 

[Aussiebikerdave]

You are a man of good faith. Your motor has to be tight. Valves have to be tight to the pistons with reduced cylinder volume due to HC pistons + 1.0mm head height reduction. Rule of thumb is .1mm off = .1 pt CR increase. 10.5 CR of Weisco BB is mostly due to a taller piston by about 1mm. You took 1mm off the head in addition. Stock these motors don't have much more than 2.0mm clearance max. Good to know you have no interference at full rod stretch at redline.

Your bike must be a blast to ride. Love the cosmetic changes as well.
Sounds like you have a stable of nice Triumphs and thanks for sharing your hotrodding with us.

In actual fact, we measured the difference in piston height with the old and new pistons joined by the small-end pin using a steel rule across the top of the pistons and a feeler guage. The Wiseco was only .0025" taller but it has a different shape crown so it was hard to compare "apples with apples". However there were other factors such as differences in the Wiseco base and head gasket thicknesses compared to the OEM gaskets. One was thinner and one was thicker but I seem to remember that the combined overall diff was .0030" less with the Wiseco parts.

I ran the bike on the dyno last Saturday and here is the result. For comparison sake, the previous figures were 71.80 hp @ 7400 and 80.5Nm at 5000 @ with modified Arrow 2:1, airbox removal kit, TB cams and head work (port&polish and 1mm shave).

With the big bore kit and associated high comp pistons (now 11.6:1 compression) bolted down tight we are now seeing 78.4hp @ 7400 and 86.6Nm (63.86ft/lb) at 5000rpm. The graph shows the previous dyno run and the most recent. The interesting thing is that the extra power is not just an extra squirt right at the top where it would be rarely accessed but a solid wedge of extra grunt all the way through from 3500rpm translating to effortless power in all normal road riding situations. Why Triumph couldn't tune their bikes (you would think the Thruxton at least) in this way from stock beats me as the motor as it now stands is more than a match to say the old Ducati 900SS and probably not far off the likes of the Ducati GT1000 in performance. Knowing these engines, reliability or longevity should still not be an issue.

The great thing is that unlike any Ducati, the bike can still be dribbled along in top gear at 50kph in town with the same docility as the standard bike and will still respond with strong top gear pull from way down low in the rev range. Yet, let the motor have it's head a couple of gears lower and it will be stroking the red line very quickly.

The little dip between 3100rpm and 3400rpm is something we will tune out with the Tuneboy software when we get some more dyno time but in the meantime, cannot be felt on the road so it's not a big concern.

 

[arewethereyet]

...oh yeah, well I added a fly-screen and new grips on my scrammy the speed gain was ENORMOUS! ...i wish.

Jammy bastage

 

[Speed3Chris]

In actual fact, we measured the difference in piston height with the old and new pistons joined by the small-end pin using a steel rule across the top of the pistons and a feeler guage. The Wiseco was only .0025" taller but it has a different shape crown so it was hard to compare "apples with apples". However there were other factors such as differences in the Wiseco base and head gasket thicknesses compared to the OEM gaskets. One was thinner and one was thicker but I seem to remember that the combined overall diff was .0030" less with the Wiseco parts.

I ran the bike on the dyno last Saturday and here is the result. For comparison sake, the previous figures were 71.80 hp @ 7400 and 80.5Nm at 5000 @ with modified Arrow 2:1, airbox removal kit, TB cams and head work (port&polish and 1mm shave).

With the big bore kit and associated high comp pistons (now 11.6:1 compression) bolted down tight we are now seeing 78.4hp @ 7400 and 86.6Nm (63.86ft/lb) at 5000rpm. The graph shows the previous dyno run and the most recent. The interesting thing is that the extra power is not just an extra squirt right at the top where it would be rarely accessed but a solid wedge of extra grunt all the way through from 3500rpm translating to effortless power in all normal road riding situations. Why Triumph couldn't tune their bikes (you would think the Thruxton at least) in this way from stock beats me as the motor as it now stands is more than a match to say the old Ducati 900SS and probably not far off the likes of the Ducati GT1000 in performance. Knowing these engines, reliability or longevity should still not be an issue.

The great thing is that unlike any Ducati, the bike can still be dribbled along in top gear at 50kph in town with the same docility as the standard bike and will still respond with strong top gear pull from way down low in the rev range. Yet, let the motor have it's head a couple of gears lower and it will be stroking the red line very quickly.

The little dip between 3100rpm and 3400rpm is something we will tune out with the Tuneboy software when we get some more dyno time but in the meantime, cannot be felt on the road so it's not a big concern.

Great post Dave and thanks for sharing your further insight into your creative hotrodding of your cool Scrambler. All valid points about the shape of the Weisco pistons and really is a system since the Weisco specific head gasket thickness matters quite a bit. I need to get my EFI T100 apart at some point to implement the changes you've made although may go with TPUSA pieces as I am a fan of Nikasil versus iron sleeves...or I may simply homebrew the motor with some milling and 790 cams, a bit of port clean up and call it good.
These motors as you have taught us as well as others need 11:1 compression and stronger cams. The motor itself is a great platform to build from....a very nice design.
Thanks again and please share your tuneboy results with us as time permites.
Best Regards.
PS: word on the street is when going to TB or 813 cams, you need to advance your ignition timing up a bit on the 865 motor to realize the full benefit. 790 motors with stronger cams natively had more ignition advance built into the ignitor.
When you get your tuneboy, be sure to put that in the mix as you tune your A/F on the dyno. The tuneboy unlike the Power Commander allows for adjusting not only the ignition map but can also raise the redline. Only thing you have to watch is dialing in too much advance with 11.6:1 compression as you want to safe guard against pre-ignition.

 

[Aussiebikerdave]

Thanks for your comments and bits of advice. Two heads always better than one... old chinese proverb!

 

[tribear]

Thanks for your comments and bits of advice. Two heads always better than one... old chinese proverb!

Ah yes, and Man making love in canoe is fucking close to water...

Incredible bike ABD. Thanks for taking the time to post the info.

 

[GuyM]

"Why Triumph couldn't tune their bikes (you would think the Thruxton at least) in this way from stock beats me..."

Same thoughts here - it's So Close to being so much more... But fairly expensive for us Triumph owners. Buying big bore kits, cams, carbs etc can cost a large chunk of change, when the power could have been built into the bikes right at the factory... Ah well, more opportunities for the hot-rodders!

Honestly, love riding my Scrambler, but with 70 - 80 rwhp & commensurate torque I'd be completely satisfied with the power...

Regards, Guy

 

[Aussiebikerdave]

"Why Triumph couldn't tune their bikes (you would think the Thruxton at least) in this way from stock beats me..."

Same thoughts here - it's So Close to being so much more... But fairly expensive for us Triumph owners. Buying big bore kits, cams, carbs etc can cost a large chunk of change, when the power could have been built into the bikes right at the factory... Ah well, more opportunities for the hot-rodders!

Honestly, love riding my Scrambler, but with 70 - 80 rwhp & commensurate torque I'd be completely satisfied with the power...

Regards, Guy

We ran the Scrambler at a BEARS meeting at Morgan Park Qld a couple of weekends ago and had a ball but there's nothing like a spot of racing to improve the breed so there are changes being made as we speak.

The major mod is that the heads are away at present getting 2mm oversize valves fitted whereupon we will be doing the proper clearance checks on re-assembly. This will probably push the output into the mid eighties. I will post pics when we get the head back. The other main mod is to replace the 4.25" rear rim with a 5" wide rim when the Excel importers receive their stock. Due to the fact the narrower rim pulls the 160 section tyre in too much it was not possible to use the entire tyre however if Rossi was riding the bike it might have been a different story! We were running Continental Race Attacks.

We even got to take home the trophy for our division... although out of the 25 or so riders in each race, only 4 or 5 riders comprised our division of Formula 4!

 

[nohawk]

Completely Badass. AussieDave you made me want a scrambler even more,one with even 70rwhp would be nice. What type of power do you think the 360 engine would make with the same mods and compression ratio?