13100 rpm fourbanger restricted to 9300 redline

[Nut124]

Strange rules. Getting 90HP at 9300 vs 106HP at 13000+ does not seem right unless it has variable cam timing. Do you have the torque, HP plots for the factory engine? What does it show at 9300?

Would it not be better to look for an engine that is designed to provide peak power at below 10000?

[ptuomov]

Strange rules. Getting 90HP at 9300 vs 106HP at 13000+ does not seem right unless it has variable cam timing. Do you have the torque, HP plots for the factory engine? What does it show at 9300?

Would it not be better to look for an engine that is designed to provide peak power at below 10000?

This is a spec series. Think of the rules as a given fact. Theology.

The 90hp @ 9300 rpm is the expectation with all the tricks applied within the risks.

[johnef]

Longer Stacks, Longer pipe and smaller diameter, much looser valve lash=kills duration to compliment the latter.

You can also offset lash per cylinder to get an extra boost. Pull out the valve seals, it will smoke a bit. Run 1 compression ring. Run the pair valve mod. Remove counter balancers if allowed.

Keep the secondary throttle-plates on it.

Airbox is a waste of time, unless you go ham and enlarge. You can add a spacer to make it larger. Remove the center support. Obviously seal the ram air system.Clean up the step on the Tbodies after the primary blades. Remove half of the shaft, radius the corners of the blades, counter-sunk screws and flush cut them. I add a 80 grit finish in the bores. Bump fuel pressure for better mist.

Not sure which year you have and is car app or bike.

600cc are sewing machines, very sensitive to friction.

We cranked 140hp out of an R6, every penny counts.

1000cc are more forgiving

[emsvitil]

Just use a tach for a 6 cylinder engine.............

13,950 rpm will show as 9300 rpm

[cgarb]

Does this engine have rocker arms? Would there be some way to modify a rocker to change the lift?

[BLSTIC]

Have you tried many of these things in EngMod4t?

Engine Analyzer is giving me results that don't quite make sense, but that's probably because I'm starting with assumptions based on parts that I can find vs measurements from the correct engine (Assuming an 08 model?)

[ptuomov]

Johnef: what is the pair valve mod? Also, since the rpm is limited to be so low, does the friction end up being as important as with an unrestricted engine?

[ptuomov]

What are the friction losses from running too much valve spring?
By my logic, 9300 rpm only needs about half the spring load on the nose compared to 13100 rpm. What would be the friction loss savings from resetting the factory springs to give only about 60% of the stock load on the nose?

Also, how about deliberately leaving a step on the floor of the intake manifolds and intake port? That is, fill the intake manifold floor with epoxy but leave the intake port stock as mandated by the rules. Could one get the step work like the tumble valve in some car engines? That is, direct the charge over the long side of the valve and get the tumble meter spinning?

[ptuomov]

Just use a tach for a 6 cylinder engine.............

13,950 rpm will show as 9300 rpm

The tech will look into the data logger and also has external rpm meters on the track. They don’t disqualify for a missed shift but if the rpm is above the 9300 rpm for more than two seconds by track measurement equipment, it’s DQ.

[ptuomov]

Does this engine have rocker arms? Would there be some way to modify a rocker to change the lift?

Direct acting bucket lifter. More lash will reduce duration.

I wonder how much low lift glow one could kill simply by “repairing” the valve job within the instructions of the factory service manual? 45 degree seat, etc.

Factory header is a ground clearance compromise I think but this engine in the car already has a completely new header sized for the lower rpms and power.

[englertracing]

Does this engine have rocker arms? Would there be some way to modify a rocker to change the lift?

Direct acting bucket lifter. More lash will reduce duration.

I wonder how much low lift glow one could kill simply by “repairing” the valve job within the instructions of the factory service manual? 45 degree seat, etc.

Factory header is a ground clearance compromise I think but this engine in the car already has a completely new header sized for the lower rpms and power.

The factory 4-2-1 is the way it is to smooth the peaks and valleys in the torque curve to to make power delivery as smooth and predictable as possible for one wheel deposition to the track often at high lean angle

[lefty o]

Also can you run two exhaust cams?
I know on some of these engines the camshaft journals and such are the same and the dwarf dirt cars and 600 sprints and lightning sprint dudes liked to replace the exhaust cams with stock intake cams because they usually had similar duration but more lift.

Maybe you want to use two exhaust cams?

That would be cheating but I'm not ruling it out!

if it is not specifically laid out in the rules, it isnt cheating!

[nitro2]

Does this engine have rocker arms? Would there be some way to modify a rocker to change the lift?

Direct acting bucket lifter. More lash will reduce duration.

I wonder how much low lift glow one could kill simply by “repairing” the valve job within the instructions of the factory service manual? 45 degree seat, etc.

Factory header is a ground clearance compromise I think but this engine in the car already has a completely new header sized for the lower rpms and power.

The factory 4-2-1 is the way it is to smooth the peaks and valleys in the torque curve to to make power delivery as smooth and predictable as possible for one wheel deposition to the track often at high lean angle

The factory 4-2-1 has a positive pressure pulse in the exhaust port for most of the overlap period over the entire rpm range the OP is interested in. Couldn't be much worse.

[Truckedup]

Do the rules say you cannot alter timing of the stock cam? Playing with lash is altering timing....Do you know what the intake centerline and exhaust centerline are in stock tune?

[ptuomov]

The factory 4-2-1 has a positive pressure pulse in the exhaust port for most of the overlap period over the entire rpm range the OP is interested in. Couldn't be much worse.

The main change they did in the first round of changes was a new exhaust better suited for this rpm range and power level and the engine picked up almost 10% more 7000-9300 average hp.