Gsxr1100 N doesn't make enough power after 10k rpm

[mx13]

Hello 

today I made one short dyno session with my 1100N stock bottom end, ported head, 4in1 system, moded ecu and the result wasn't good enough 130.3/9800 rwhp and 105.6/7400 rwnm.
Here you are the graph:



I'm currently running stock cam timing, but I plan to retard the intake one. Hope this will move the tourge late in RPM and wil lift the Hp graph after 10K . 
What best LC with stock cams are?
Thanx in advance!

Regards,
Martin

[oilyspanner]

Hi Martin
That's not a very good return !
I wouldn't want to spin the crank past a true 11k revs, people have fitted the 750 ecu box and broken the crank. A true 11000 revs would be 12000 revs on the standard tacho, they over - read. If you have the 1100N head, a shim is likely to be spat out at some stage. If you regularly rev past 11000ish revs you will ruin the motor.
A standard M/N with the derestricted silencers fitted will make 128 - 130 rwhp, that's assuming the jetting, valve clearances, air filter and engine are good (there are so many variables), dynos often read differently. Mine made 132hp with a Cobra pipe and jetting changes a few years ago. I have found the Pipercross air filter to flow the best (in box filters), it flows so well I had to fit a stage 3 Factory Pro jet kit
You haven't got an air/fuel ratio included with the dyno run, it could be running rich or lean.
The standard cams will make peak power at about 10k and peak torque at near 8k, so that seems about right with yours.
The oil cooled 1100 motors aren't designed to spin like a modern engine, you will have a BIG engine failure if you rev the engine like a 750 or modern 1000. These engines make big torque with decent hp.

[oilyspanner]

I've had further thoughts about your engine, there aren't so many tuners who know how best to get good overall power from an O/C head. Remove too much material and you can lose power, getting good flow around the port bowl (where valve guide shows) helps top end without hurting lower down. You've lost torque across the rev range.
Check jetting, valve clearances, state of filter for a start, the engine could be worn - check compression.
A late 1127 with only an Akrapovic fitted can give 133rwhp - this from their own site, they are normally pretty fair with their figures. Many owners fit dual pods and ditch the air box, this can add to the top end with a stage 3 jet kit.
Over 20 years ago people use to get 1100s to rev higher with the 750 ecu - the cranks fracture and rods will go too. The standard rev limiter comes in at 10800 revs - not the 11k odd that's marked as the red line.
If you have fitted an earlier 1127 head, they were designed for 36mm carbs, so careful matching up needs to be done from carb, boots to inlet port, all nice and flowed with a taper into the port bowl - no steps.

[mx13]

Hello,

yes pistons and ring are gone, 9bar compresion the engine has 117000 km on it. Stock pistons and rings inside, but the head is done well nice 3angle seat job, the port's floor stays not touched, guides gone and nice D shape on short radius. I am using stock air filter with stock jetting with lifted needles. Now winter is comming and the engine will be rebuild. I plan some mods, bronze/berilium seats, bigger valves, and head skim for additional CR, a good setup after break in and hope for few more HP/hope for 140-145/. Anyone with expiarance with best LobeCenters for this head?

Regards
Martin

[oilyspanner]

Hi Martin
That would explain it ! The engine is allowed to be slightly tired at 70,000 odd miles.
Sounds like the head is good, it's all careful detailing stuff. A fit M/N engine with 40mm carbs, full system, good jetting and porting should give over 140 rwhp no worries.
To maximise your mods a free flowing filter and rejet would be good. I kept the airbox to maintain ease of dialling in the 40mm carbs, the Pipercross replacement filter is large and very free flowing, it has a huge opening to the filter itself, it made my settings very lean and that was set-up for a k&n filter. By fitting a stage 3 Factory pro kit (meant for dual pod filters)- I fitted the 150 mj, the richer jet needles supplied, a bit of fiddling with fuel height (float bowls)and 3 turns out on the pilot fuel screws has given me very strong delivery from 2000 revs up to rev limiter.
With standard 1127 capacity, one tuner got to 154bhp, without race cams, but larger inlet valves (only 1mm extra I think), porting and good fuelling for race exhaust, head mods and air filters.
OS

[oilyspanner]

I've just found the article by the tuner chap I mentioned - really good for the best areas to tune for extra power.

 Dynos give different readings, but these figures give a decent idea what to expect.

Dwayne and I have been racing GSXRs for over 10 years now, and we have seen and tried it all. So believe me when I say that the head is the very first place you should spend money, even before pistons.

I will give you some example numbers from a personal street bike that we did a bunch of experiments with several years ago. The bike had 40mm Mikuni flatslides, a full Race-only Yosh exhaust, and a Dyna 2000 ignition

Stock 1127 engine with degreed cams, 750(oversize) carb boots, Mikunis: 130hp

Stock 1127 pistons with a full port job and 30mm intake/26mm exhaust valves, stock cams: 154hp

1216 Wiseco pistons with the same head/cam combo: 161hp

1216 Wiseco pistons, same head with .380" lift cams: 169hp

1277 JE pistons, head shaved to increase compression, same head and cams 180hp, sidewinder exhaust

1277, same engine except for .425" intake cam: 182hp

1277 same engine, except for oversize intake seats, 31mm intake valves, and the head slightly reported to take advantage of the larger valves: 190hp

As you can see, the oversized valves and port job were worth 24hp alone. It took 5mm oversize pistons, oversize sleeves, bored cases, huge cams and a sidewinder exhaust to exceed that level of power increase.

If you add in the gain from the 31mm intake valves, and you have a total power gain of 30hp from just the head!

To put it in perspective, I have seen 1340 big blocks with ported stock-valve heads that barely broke 150hp. That same engine, with a stock head, only made about 144hp.

Also, I would stay away from the slingshot head, unless you are going all-out with a serious engine. The carb boots for the Slingshot head are only made for 36mm carbs. The oversize boots from the 90-92 750s are made for factory 38mm carbs, and are way bigger, and allow for a straighter port design. The problem is, the 90-92 boots don't fit the Slingshot head. They bolt up, but they are about 3/8" too low, so they actually hurt airflow. Plus, the raised ports on the Slingshot head put the carbs so high that they hit the frame in an 1100 chassis.

Also, the Slingshot head has such a small combustion chamber that the piston domes must be hand-fitted or the engine won't even turn through. And the valve pockets must be cut deeper in the pistons to accommodate a Slingshot head as well.

The best head to use, unless you are building a high-dollar race head with weld-on spigots, is the 91-92 1100 head. It has a nice raised floor entry into the short-side radius on the intake side, and is worth 4-6hp over the 86-90 1100 head. And the big carb boots bolt up perfectly.

Now if you want a 33mm intake valved, offset-guide monster head, capable of over 210hp with a stock crank, then the Slingshot head is the way to go. That what Dwaynes brother TJ has on his Heavy Hitter bike.

Does say that the 91/92  1100 head is pretty decent and well worth keeping for the majority of tunes .

[mx13]

Hi oilyspanner,

such a helpful info is that!

I've found used block with pistons from gsx1400 in reasonable money, so I'm wondering is it possible to use those 81mm pistons in my engine /overbore stock barrels/ ? With set of new piston rings 1184cc would be nice, isn't it?

Regards,
Martin

[oilyspanner]

Hi Martin
As I understand it the GSX1400 is an entirely different engine to the earlier SACS engines - had a 9mm longer stroke too, that's a lot to machine off ! I think there would be a load of work involved to make any parts fit.

Keep us updated
OS