Ring Gap, Stock Valve Springs/Valve Questions

[rider384]

Finishing up my built 1216 and wondering about ring gap and valve springs/valves. Eventual goal is 400whp on pump gas. 

A couple questions I have:

1. Unsure of what to set my ring gap to. I've attached MTC's technical sheet but I'm unsure of what category I fall in to. Bike is primarily street ridden with plans for standing mile stuff (non-competitive, for fun). So it has a huge mismatch of power to use case, making me fall into several different categories on the chart. Thinking 0.0175" top and 0.019" bottom, which corresponds to "circle track/drag race" category. Considering going up to 0.019" top and 0.021" bottom, which sits in between "drag" and "blown race only". 
2. At what boost level does the stock valvetrain start floating valves?
3. At what power levels on pump do the stock valves start to burn?  I know it varies heavily from setup to setup, but rough ballpark. 

Specs:

Engine currently has:

• MTC Turbo Pistons w/ tool steel wrist pins
• Maxpeeding rods i-beam rods
• APR2000 rod bolts
• APE heavy duty case/cylinder & head studs
• And non-power stuff like new bearings and o-rings and such, etc. 
• CR somewhere ~9:1, might toss a spacer plate in it to get it down to 8:1 or so, depending on how the detonation situation is when it's running. 

Turbo kit/Electronics are currently:

• Twin K04-015s
• EFI Conversion run via Microsquirt
• LS Coils
• 3" turboback with cat and muffler
• No intercooler now but obviously planning on adding a decent sized core once I figure out where to put it/how to fit it. 
• Possibly water/meth injection, again depending on the detonation situation as I push the power levels higher and higher

[Fazz711]

Not an expert but high performance street\strip sounds more like what you say you will be doing

Valve float is more about revs than boost I think.

[Gixer1460]

48 minutes ago, Fazz711 said:

Not an expert but high performance street\strip sounds more like what you say you will be doing

Valve float is more about revs than boost I think.

With your target HP, I think you'll struggle on pump gas in CA! Way back my GSXR made 370hp on 110 RON race gas and it is a 1460! Boost was maybe around 2 bar! 

Boost affected valve float can be down to either piss poor spring pressure or excessive boost. With GSXR sized valves I think you'd be into VERY big boost or you'd forgotten the inner spring from a dual spring set up! Using big lift / duration cams doesn't help valve cooling - minimising seated time is what burns / melts them. It doesn't take much either to start making the stems malleable, then the heads snap off + carnage!

You are trying to do two different things with one bike . . . . . . a 'ridable' street bike ie. good manners, doesn't stall or over-heat during use and also a Top Speed miler. It may only be 'for fun' but the engine don't know that - all it knows is you are asking for WOT for a mile+ and that is a lot of power / heat generation and for that application cooling = drag = slower!

As regards ring gap, a 'maybe happy medium' would be 0.006" / 0.006" - it may smoke a bit but shouldn't seize especially if you do make the boost for 400hp.

[rider384]

1 hour ago, Fazz711 said:

Not an expert but high performance street\strip sounds more like what you say you will be doing

Valve float is more about revs than boost I think.

Boost on the back of the valves can contribute to valve float. My turbo LS car floated at anything above 7psi on stock valve springs, but stock springs on the LS are incredibly soft. Though yes, it's usually more related to revs but boost can contribute as well. 

42 minutes ago, Gixer1460 said:

With your target HP, I think you'll struggle on pump gas in CA! Way back my GSXR made 370hp on 110 RON race gas and it is a 1460! Boost was maybe around 2 bar! 

Boost affected valve float can be down to either piss poor spring pressure or excessive boost. With GSXR sized valves I think you'd be into VERY big boost or you'd forgotten the inner spring from a dual spring set up! Using big lift / duration cams doesn't help valve cooling - minimising seated time is what burns / melts them. It doesn't take much either to start making the stems malleable, then the heads snap off + carnage!

You are trying to do two different things with one bike . . . . . . a 'ridable' street bike ie. good manners, doesn't stall or over-heat during use and also a Top Speed miler. It may only be 'for fun' but the engine don't know that - all it knows is you are asking for WOT for a mile+ and that is a lot of power / heat generation and for that application cooling = drag = slower!

As regards ring gap, a 'maybe happy medium' would be 0.006" / 0.006" - it may smoke a bit but shouldn't seize especially if you do make the boost for 400hp.

Yeah I'm asking a LOT of the motor - definitely a "split personality", so to speak. That's why I'm so confused on what I should gap the rings at. 

In regards to the CA gas, I'm hoping that an eventual water/meth injection setup will get me closer to my goal. I definitely don't expect to see 400 on solely 91 octane, just gonna push it higher and higher until the detonation is uncontrollable and go from there. Or perhaps an E85 tune for high boost and 91 with lower boost on the street... Not sure. Either way this bike has always been an experimental platform to mess around with to see what I can get away with. 

Thanks for the advice! A smokey startup is fine, so long as it's not leaving a blue cloud behind me once it's up to temp I can deal with it. 

 

Edit: oh, and it's naked and I'm 6'0 @ 150lbs so standing mile is going to be a lot more about my strength limits than the bike's at that point

Edited August 23, 2022 by rider384

[clivegto]

400hp is a lot on pump gas. 

[Fredrik_Steen]

Looking at the compressor map for the K04-015s you are on the edge. A decent work on cylinderhead would be nice so you don't need to push beyond 2bar. A lot and a lot of intercooling are a big must. 

ignition retard are your best friend to reach your goals. Don't push to mutch boost in the peak torque curve - be wise with your boost controller.

You really don't want the rings to bottom up at any point 

 

Nice experiment you are running, keep us updated with progress later on

[rider384]

On 8/26/2022 at 12:53 PM, Fredrik_Steen said:

Looking at the compressor map for the K04-015s you are on the edge. A decent work on cylinderhead would be nice so you don't need to push beyond 2bar. A lot and a lot of intercooling are a big must. 

ignition retard are your best friend to reach your goals. Don't push to mutch boost in the peak torque curve - be wise with your boost controller.

You really don't want the rings to bottom up at any point 

 

Nice experiment you are running, keep us updated with progress later on

I'm super skeptical that the turbos will hit 400whp on their own without some help, but we'll see. Looking at the compressor map, it should be possible but it just comes down to controlling the heat and detonation. The compressors might be out of their efficiency range to the point that the heat will be too much for any motorcycle-sized intercooler to effectively control. 

Though if it comes down to that, I have an Eaton M62 ready to be installed and fed via the turbos for a compound boost setup. That's a bit further down the line though, and dependent on me not sending a rod into the stratosphere with just the turbos. 

[Fredrik_Steen]

27 minutes ago, rider384 said:

I'm super skeptical that the turbos will hit 400whp on their own without some help, but we'll see. Looking at the compressor map, it should be possible but it just comes down to controlling the heat and detonation. The compressors might be out of their efficiency range to the point that the heat will be too much for any motorcycle-sized intercooler to effectively control. 

Though if it comes down to that, I have an Eaton M62 ready to be installed and fed via the turbos for a compound boost setup. That's a bit further down the line though, and dependent on me not sending a rod into the stratosphere with just the turbos. 

Do you have the compressor map for your turbo to upload here? 

That ones i found on Google seems to only support about 1,8bar 

 

Think you will be looking at a water to air intercooler system for your setup.

The rods you have are awesome