This is a question for the hardcore engine performance gang out there. I'm new to forums in general but not new to Suzuki, been building and playing with the engines since 1991. But this one has got me stumped.

1990 G16 8 valve, this engine is built to the max..
balanced, blueprinted, ported polished, nitrided, beam polished, crank knife edged it's got it all.

9.0: compression ratio
Stock camshaft/rockers
Calmini tri y header
Custom hand made intake
(2) CD 175 Stromberg carbs
Crank fire ign..max advance 36 degrees |removethispart|@ 7000rpm

   The engine was designed with the intent of producing
100hp |removethispart|@ 6000rpm/105 ft/lb of torque |removethispart|@ 4500rpm approx
all systems have been throughly checked and are operating perfectly...
    I've built 5 other test engines, all 1300's same combination, never had a problem. This 1600 has got me stumped.
    On the test bench, under load, I'm out of power |removethispart|@5000rpm. The 1300 * valves peaked at 80hp |removethispart|@ 6500 rpm. I really want 6000rpm.
    I repeat all systems ignition, carbs, exhaust, compression are perfect. I am thinking ether I have installed the cam out a tooth (unlikely but not impossible) or I need more cam...your thoughts.

I specifically used the stock cam as it should have put the power and torque where I wanted it.

    This engine is being used on an airboat, and I am loading using a prop designed for the application.
    I am also building another same spec for my 2WD tracker I am building for my daughter.

Zaggy
 

The 1300 * valves peaked at 80hp |removethispart|@ 6500 rpm. I really want 6000rpm.

what does the * mean

Did you use 1300 valves or a 1300 head ?
if this is the case I see a flow thru the valve
problem, 1300 valves are a little smaller than
1.6L valves

Your list of engine mods looks impressive, except
you skipped a few performance mods, like a Cam
and some higher compression pistons, 9.0:1 is
below stock (9.1:1) and if you ported too much
with small valves and/or a stock cam you don't or
won't have the desired intake charge velocity to
make the power you seek.

Get back to me or post some more details,
I might be able to help your thirst for power

Wild

I thought stock compression was 8.9:1

Thank you for the response wild...
The * was a typo, should have been 8 valve.

The head is a 1600 8 valve, stock valves. Porting was a clean up and polish, not apprecaibly increasing the size of the runners. Light pocket porting in the valve bowls.
    The valves and seats are a five angle grind that we have played with, gives good flow, really good life.
    The camshaft is the stock 1600, chosen as it makes peak power at the target rpm and peak torque should have wound up where I wanted it. I'm not after monster power...just good power, extreme reliability at 4500-6000 rpm, thats why all the mods.
    Once the engine reaches 2/3 throttle it is at 5000rpm, opening the throttle more gets "0" more rpm. There is no ignition break up, compression, valve clearances etc all one the spec. It runs really well at 5000rpm, it just won't go higher.
    The plug colors, timing curve, max advance (36 degrees) are all on the money, spark intesity you could almost weld with.
    All systems excellent. After working over the system the last 10 days I'm narrowed down to three things possible...
- Carbs waaaay to large, but I don't think so from the
  throttle response and plug color, but possible.
- I've got the cam advanced 1 tooth, I'm an experienced
 builder so I don't think so...but everyone makes
 mistakes.
- Not enough camshaft for the combination. I'm not after
 big rpm (over 6000rpm) power so I felt the little more I
 wanted would not need an aftermarket cam, but
 maybe I'm wrong. The carbs normally feed a 2.0l car, maybe the effect of reduced velocity and stock cam are fooling me. But again, excellent throttle response and it runs so good.
    Has anyone every tried retarding the stock cam 1 tooth?

I'm certainly open to any observations as this one is a bit of a mystery.

If I don't figure it out soon I'm going to pull the engine back out and start rechecking cam timing marks etc...but it runs so good I thought I'd try the forum cause I must be missing something.

Zaggy

The difference in the engine size from the
carbs intended engine and the 1.6L Suzuki
engine are not an overkill in my opinion, I do
however think the stock cam is really peaked
out at 5000 RPM, and you would see some
increases with a performance cam.

I had the stock cam reground by Engle Cams
in Santa Monica Ca. they can't change the duration
much, but the lift is increased, I wish I could find the
new spec that it is ground to, but I have moved 2 times
since and never recalled seeing the paperwork, so
without using a dial indicator and a degree wheel
I would be just guessing, but it seems to me the
lift was increased by about .125/inch  made a big
difference in power, I don't think I could make 100
HP with just a cam, I think you will need high CR
pistons and a better cam, remember you want to
see 6000 RPM, so the cam needs to be more wild
than you think.

Also an airboat runs at a more or less constant RPM
as compaired to a road vehicle, so you can target
a specific RPM range, like 5500-6000 and have a cam
that really works well there.
The other thing is I don't know what your custom
intake looks like, did you build the runners to maximize
the RPM band you want ?

Shorter runners like the stock TBI intake are for
a 3000-4000 RPM range, which is where the Track/Kicks
spend most of their freeway speed life.

I have some tables and charts to help dial in tuned
length runners and camshaft profiles that will get
you close to where you want that engine to run.

My best guess is that you are going to get 85-90 HP
out of your setup, without a cam and higher CR you
are basicly running a stock 1.6 with a header

What is your reduction ratio to the prop ? 3:1
what pitch ? is it too much for a 100 HP engine ?
How many blades 2 or 3 ?
So many variables with this application

Wild

I agree with Wild that you should really look to doing some cam work as these motors respond well. Isky do a torquer cam for the 1300/1600 8v motor but there should be a number of alternatives then look at making/buying an adjustable cam gear to put the power where you want it in the rev range. I also think an increase in compression is required.

Thanks Wild and CJ for your replies.
    Is the G16 that much more sensitive to the cam than the G13? The reason I ask is this is the 5th engine of built over the last number of years on this project.
1) Stock G13 8valve, dyno'd* to destruction as baseline
   - proven 68.5 hp |removethispart|@ 6000rpm as claimed by Suzuki in
     Canadian Metro (ok thye claimed 70hp)
2) G13 8 valve built same spec as this G16 but with (4)
   motorcycle carbs and modified stock distributor, stock
   G13 Metro camshaft
   - tested to destruction, 94hp |removethispart|@ 6400 rpm*
3) As above rebuilt and tested on airboat (still going
   after several years)
   - proves out at 85hp |removethispart|@ 6000rpm based on prop
     being used
4) G10 (early series) turbo (thought it would work out
   lighter, I was wrong by a bunch)
   - about 90hp |removethispart|@ 5800rpm based on known prop that
     was being run based on know prop that was been
     run. (but boy did it end up heavy)
5) This engine..
    Wild, you asked about the drive, it's 2.222:1 cog belt
    the prop is 3 blade set to the same spec as used on
    Rotax 912S (claimed as 100hp from Rotax)
    Based on the prop rpm I am getting I would est I am
    currently getting 85-90 hp |removethispart|@ 5000rpm, max it will
    turn. The combo should make a great engine for the
    rag top I'm building for my daughter.

    I've built alot of engines over the years (raced everything from 850cc FIATs to 360ci Chevy's in Sprint cars) including a bunch of various Japanese makes. Got turned on to the Suzuki's after taking them apart in the Auto recycling business (liked the way they were made).
    That's why I'm surprised that this one is apparently being so cam sensitive. The L-16 Datsuns and 3TC Toyotas always seemed to have more than enough cam at this level of mod.
    Is it your experience that the G16 is more cam sensitive than the G13 and other engines I've mentioned. Oh yes I'm not sure I made myself clear..the intake system is two 1 3/4 inch inlet Stromberg side draft carbs.  Quite a jump over the stock throttle body. The runners are about 3" long feeding into a balance tube then to the carbs (2), it's a compromise to fit the engine bay. (would have liked about 6" according to my math)
(*Dyno was a local Super Flo computerized and corected to sea level).

Thanks again for your thoughts, it's really appreciated.
I'm used to ether building nice stock motors or full tilt race engines. building this realitivly low rpm mid range engine is a new experience. This project has cost me a fortune but I gues it keeps me out of the bar.

Zag

Well lets see, the 1.3 engine is a much shorter
stroke, so they tend to rev quite a bit more.

the 1.6 is a stroked 1.3, the piston is 1mm larger
bore, but 15mm longer stroke.

I put a 1.6 head on a 1.3 engine, didn't really do
much, the valves are a little larger, ohh I guess
about 2mm, but I don't think the lift is much different.

a 1.6 with a basic cam profile from a 1.3 would be a
good torque maker.

I added a turbo to a 1.6 with my special cam and
got 93 MPH in the 1/4 mile on 30" tires with 5.83
gears, with a vehicle + driver weight of 2700 Lbs this
equates to about 150 Crankshaft HP, and 125 to the street at about 8 PSI boost.

I think you could use a high lift cam, not the off the
shelf Calmini or Hawks cams, as these are designed
around the use of the engine in a 4 wheel drive and
off road appilcation. I would contact a reputable
camshaft grinder and have one ground to your specific
RPM and HP needs.

The Cam, Intake and exhaust is what makes a motor,
all the othe stuff like the knife edging and nitriding is
gravy over the heart of the engine, and I know a stock
cam is not going to give you the HP you want without
some sort of supercharging.

Your HP specs and my guesstimate were pretty close
so I think your cam is timed right, you could play with
a little retarding of the cam and report back any increases
or losses, this would be a great tuning guide for tweeking
the power output of these little engines, the Prop works
like a dyno, which none of us have really any access to,
at least without paying lots of $$ for test time.

Advance the cam 1, 2, 3 teeth, and then retard and
see what happens, if I recall correctly retarding the
cam will help the RPM band move up, see if you can
get your RPM and HP to climb, then try some other
cams if you want.

I have my special cam that is not going to be used
in the 16V engine I'm redoing, I would be interested
to see what it does in a dyno situation like you have

Wild

Someone on here did retard the cam a tooth and reported a very noticable gain in performance. You might be able to find the thread doing a search. I don't think theres a lot of difference between the 1.6 cam and the 1.3 cam in terms of duration. I think thats why the 1.6 makes its peak torque much lower down so you aren't likely to get the same kind of rpm from the 1.6 without cam timing changes.  I would love to see pics of the twin Stromberg set up.

Thanks for all the resposes guys I really appreciate it.
    I will post pictures of the carb set up as soon as I get the engine working right. I hate showing stuff that doesn't work to my expectation. Based on the fighting I had to do to get them to work right I feel one size down
(CD150's) would be better for the street.
    As for my glitch...after doing more runs, advancing and retarding the ignition (dramatically) and the advice I've gotten here I am going to do a cam swap. The goal is still the same 100hp|removethispart|@6000, peak torque at 4500rpm or so. The combo I'm running now is what I'm going to put in my daughters rag top. (but with the smaller CD150's) I think it will be more than enough for a 16 year old. The way the long block is built I don't think she will ever be able to hurt it.
    Any suggestions on camshafts to meet this goal would be great.

Thanks Zag

Someone on here did retard the cam a tooth and reported a very noticable gain in performance. You might be able to find the thread doing a search. I don't think theres a lot of difference between the 1.6 cam and the 1.3 cam in terms of duration. I think thats why the 1.6 makes its peak torque much lower down so you aren't likely to get the same kind of rpm from the 1.6 without cam timing changes.  I would love to see pics of the twin Stromberg set up.

I retarted my cam/crank one tooth and noticed my power band moved a bit and increased. Now it starts better, idles better and Pulls like crazy from about 4500 to 5500. I put it back to stock and tried to tune it to get the same power but just couldn't, So I took it back a tooth again.

Thanks for the response Humzuki.

    I thought about just playing with retarding the belt, but I'm thinking that to get to the 6000rpm target it won't be enough.
    Any thoughts out there. I feel I'm close to my power but need the additional rpm.

Zag

For your application I assume that you generally run at a fairly constant rpm. You may find that a tuned length 4 to 1 header would suit your needs better much like your tuned length intake manifold. The tri-y is great for our application offroading but may not be what you need especially as you are searching for power at the top end of the rev range.

Thanks for the input CJ

    You're right that the rpm remains fairly constant...
4500-6000 range. At the same time I chose the tri y as a way of maintaining the torque at the lower end of the range. With a prop you want to be able to get "on the step" per say right fast, but have the torque maintained a little lower so you can maintain a fast cruise by using a coarser prop pitch...it's a compromise. For the rag top (2wd, lowered) I'm building for my daughter, it means really good throttle response and mid range torque.
    "Wild" was right on the money when he said a prop make a great dyno. It lets me check loaded throttle response and get good estimates on peak power by comparing to know combinations.
    This combination has given me almost everything I want (except peak power where I want it) and I think it will be a good driving combination. Right now I'm researching camshafts and have found a 226/395 duration cam with about .050" more lift than stock that is looking like it will fill the bill, but I'm real tempted to try Calmini's cam  with 288/288 duration. Has anyone out there tried it and what kind of rpm were they able to get?
    I'm thinking with the extra breathing from the twin Strombergs it might get me the 6000rpm and maintain high torque at the 4500-5000rpm range that will let me run a higher pitch setting for cruising. Hawk has a 272 cam they recommend but I don't have the exact specs yet (tommorows project).
    Any other input out there?

    The other thing I noticed and would like some opinions, I was going through "Readers Rides" and noticed fantastic  efforts in suspension technology and design, but not too many get involved in building more power. I'm an old road racer, rallyist, drag racer and thought that unusual, or am I just behind the times?

Zag

    Againthanks to everyone for their input.

On my Camshaft usage chart I have
listed 260 duration |removethispart|@ .050 lift is good
for 4000-7500 RPM with a rough idle
and 250 duration |removethispart|@ .050 lift is good
for 3500-7000 RPM with a rough idle

This might give you a starting point to
choose a cam for your project

Wild