If it wasn't obvious before.... oh, it will be now

 

Dang, almost like you could make those runners curve out in a half circle and cross under the plenum and it would fit under the hood .

 

Chrysler - in the sixties.

 

Those Max Wedge ultra long runner intakes are possibly, IMO, the best looking intakes of all times. I'm a sucker for ALL the long-runner intakes, though...

Adam

 

The weird thing to me, is that with that intake's runner-length of 30 inches and the port centerline of the LS head around 4", you've got a total runner length of 34 inches which means the 2nd Harmonic wave is that HUGE hump that we're seeing from 3,455 -4,000ish. ->It's cool to see the stronger 2nd harmonic wave (+10%) vs. the +7% 3rd harmonic wave that we normally see with TPI intakes, but I'm getting distracted...

To pull up the dynograph this link will take you to the exact second it's displayed:

The weird thing to me is: WHAT is responsible for the peak out at 5,000 RPM?
The TPI-like 3rd harmonic would be around 2,600 - 3000 RPM on that engine and the baby 4th harmonic bump at 2,000-2,250ish.

Is that final peak just the negative effects of the ill-timed 2nd wave dissipating and we're finally seeing just the engine combo's natural hp peak disregarding the intake wave tuning? (Head intake port volume, cam, and exhaust system, disregarding wave tuning would naturally peak around 5,000 ish RPM?)


Adam

 

That same motor went to 6500 rpm with the short runner. It dies early because long runners cant keep up mass flow demand. Suck through a 1” pipe thats 3” long vs one thats 30” long, its harder to over come length. More losses

if you made those runners larger in area the peak would likely creep higher but still be subject to tuning effects of the length

 

Thanks. That finally makes sense. I should've compared the before and after more closely vs. just focusing on the dyno test with the Skyram.


Adam

 

All it needs is a little port on the side connecting all runners close to the base that opens up at 4500rpm to bypass the long runners, EFI doesn't care where the air comes from, whether its a vacuum leak or not makes no difference when theres no carb to disturb

 

Wow. what a creative idea! Definitely makes me think..


Adam

 

basically honda vtec

 

Honda did that back in the day starting around 1987ish on EFI cars. Here is an example


VTEC is different it is actually an extra camshaft lobe on a rocker that does not engage until higher RPMS that bypasses the other lobes allowing two cam profiles

 

Right vtec itself is cam phasing but im talkng about the booost in performance when it kicks in lol. When the runners switch you should feel that

 

You do for sure, I remember how it felt in both my Accord and solara. Also my integra with both VTEC and varied runners.

 

Toyota did the same kind of thing with their sequential twin turbo setups for 2jz supra engines 95-02. It would feed a single turbo then open a second set of turbo/plumbing once the first was 'used up'.

Its a fairly consistent theme of automotive manufacturer's trying to get the most out of their setups. Which is good for us when it works I guess. The downside is increased complexity- most people would just remove all the actuation 'mess' and use a simple design for reliability. For example single turbo on a Supra. Or removing direct injection in favor of port overhead injection.

I prefer simplicity to high efficiency, but we don't always get that option

 

Properly tuned you should not feel the runners "open up".

 

yeah totally depends on the control strategy of the runners. If it just switches between two sets of lengths at a certain rpm, it may be obvious. True variable control runner would require runner length that can change with rpm like an accordion lol not sure how one would do that

 

Didn't the LT5 have flaps in the runners? or was just that just the dual injectors

 

Like this: https://hotrodenginetech.com/hardcor...ers-challenge/


Adam

 

Well there is one overlooked aspect in all of this and that is variable cam timing.

For example on Honda S2000 engines the cam phase can move with RPM increase. This will generate an absolutely perfectly flat VE and torque curve- the engine is able to breath at 100% for all RPM intervals.

I've seen it on a dynojet back in like 2005 from a stock S2000.

The moral is, if the runner can support the raw flow rate, and you can control the cam, you can tune for perfect VE without having to worry about the effect of runner length. I think its easier to move the cam in real time than the runner length so most manufacturers are going this route.

 

Moving the cam becomes more dangerous as you get into more aggressive cams, though. Variable length runners won't bend a valve.

 

Well I just assume if they design an engine with cam control they know how far they can go each way. And if you own the engine and plan to upgrade the cam you've used a cam degree wheel and measured the clearance of the valve and spared yourself some extra room for just in case kind of thing. The valves on modern engines generally don't need to open very far anyways because modern head design and specifically 4-valve overhead is extremely potent even with low lift. Its certainly a thought to consider when you own and tune that type of engine, but not a concern if you are paying attention. Furthermore with the affect of forced induction in reliability applications we generally only use low lift cams anyways.

For example my 5.3L I chose a very low lift cam and slow ramp because the cam has very little influence on peak power, the turbo makes the power not the cam. Actually a larger cam would reduce power and hinder power because it would cause the engine to flow more air and according to the compressor map that will put the turbo into a region where it is less efficient and out of breath. Most modern turbochargers are really effective only once they reach 2.5~ pressure ratio so this is a specific target minimum and often requires restricting the engine's breathing to acquire the max performance from a turbo of the correct size for daily driving (not oversized as in drag racing- different thing)

Heres the map so you can see what I'm saying


See how much more the turbo can flow if it will reach 2.6 to 3.0 pressure ratio?
This is where you want to be to take full advantage of the turbocharger. When I Raise the boost it will scale somewhat linearly to the right side and the turbo will support more and more power as boost is increasing.

If I upgrade the cam/head/valvetrain/intake/etc... The boost will drop at the same flow rate, pushing the turbo off the map to the right at lower pressure ratio values. This will necessitate a larger turbocharger install, which will increase wheel mass, which will reduce spool character, which is unwanted in daily driver applications.
People that miss this aspect of turbocharger setup will never realize how much spool character they are missing by oversizing their turbos to run well at low pressure ratio values, due to upgraded engine breathing mods. It is a V8 issue mostly because of the displacement. Most 2L to 3L size engines are not making enough power at 3.0 pressure ratios (roughly 25-26psi of boost in the intake manifold) to destroy a stock engine, no matter what the head can flow. A 300+ cubic inch engine on the other hand with upgraded head and 25psi of boost we are talking 900 to 1200+ horsepower, out of range of particularly modest setups and especially daily drivers that wish to utilize pump 93 octane fuel.

Just as an aside here is a 34psi of boost on 2L of displacement using 93 octane fuel
https://www.evolutionm.net/forums/ev...l#post11872919

 

yeah its a balancing act, but for most ls combos using 5.3/6.0 stuff thats popular, bigger cam makes more power on same or less boost, on the same turbo to a point. Theres a few variables but comparing something like a stock cam to something with 220-224 deg duration, .575-.600” lift of most popular turbo cams, you see substantial gains on most street combos without spool issues. Its likely better to run less boost to make more power on a pump gas driver. You would need less intercooler size to remove the heat, and more na power off boost should improve drivability and response. It just makes sense, more na power you can make, more power with boost. As long as turbo has the room to operate. Its all in the entire combo and goals

drag racing is usually always maxing out the turbo. You need smaller turbo for response, but need to turn it hard to make power. Sometimes class rules limit the size. Most guys always push to maximize their setup, not focus on peak efficiency. If the compressor operates at 80% eff island or 65% doesnt seem to matter when on good fuel. Extra heat sucks abit of power, but you have good response and good intercooling most of the time.

 

If the turbo is sized correctly it won't make any extra power using a larger cam- only less, because it will now run right off the map as boost is reduced from some previous setting. A proper sized daily driver turbos runs right to the edge of it's map so the minute the cam is upgraded the turbo needs to also be upgraded which kills spool. I will elaborate in a min

This is a myth
Actually Boost number is irreverent. The intercooler materials has a heat capacity, a heat dissipation rate, surface area, etc... which is constant and capability is mostly based on the mass flow throughput, not the boost number or temperature input. It is far more important that the efficiency of the compressor be high, no matter what boost or outlet temperature, because compressor efficiency directly correlates to density per unit mass which is afforded some rate of Kinetic Energy.

In other words if we put in 50lb/min of air at 20psi or 50lb/min of air at 10psi and if the compressor efficiency is the same for both then due to the laws of thermodynamics the outlet temp of the intercooler will be same regardless of inlet temp because the mass flow is the same and compressor efficiency is the same. And since compressor efficiency always peaks around 74 to 77% no matter what size or style turbocharger we can treat them all the same with respect to dialing in efficiency for a given combo- the only difference being that modern turbos will simply flow more at higher pressure ratios, making a smaller turbo work superior to a large turbo on a setup which can achieve 2.5 to 3.0 pressure ratio without falling off the edge of it's compressor map.

This is the main mistake I see people make. They don't properly estimate where the engine is going to operate at a steady state output.
Also I never said use a stock cam- nobody should ever use a stock cam. The cam always need tailoring to the engine's use. But that doesn't mean larger than factory lift or faster than factory ramps. The key to getting a stock bottom end engine to live for 200,000 miles at 1000rwhp is using a stock ramp and nearly stock lift to preserve the valvetrain- no matter what you or I think that does to the power it cannot be argued that the valvetrain will last longest with these things in mind. Therefore we do it no matter what we believe about boost or heat or whatever

I'm sorry this is also backwards, I'm not sure why you would say this. I'm not picking on you, I swear. I hope you know I want to educate and not trying to just show off some BS.

Daily drivers max their turbos- run off the edge of the map. This minimizes the wheel mass which maximizes spool. All factory turbos for 2L 3L JDM engines for example, skylines, supra, silvia, rx7, whatever. They are all very "small" and run right to the edge of their maps with just stock cam/head. This allows the tiny engine to boost very quickly and easily by using a small wheel. Modern turbos have improved wheel designs, they flow more at the same weight, so we can bump the power significantly without sacrificing spool even with such small displacements. However the same rules still apply: You want to run to the edge of the compressor map "Max out the turbo" because this ensures you are getting fastest spool response character and not wasting any wheel mass.

Drag racing is quite different. When we drag race the engine is able achieve a steady state output of some HP number- for example 1000rwhp like straight line across the top of the graph. That causes the turbo to sit on some steady spot in the compressor map the entire time, like a boat at constant WOT. Therefore we would desire a turbo which can steady state right from a center island of the compressor map- basically the middle. So for example if I want to drag race with 1000hp to the tires I will choose a turbo which support 1400-1600hp so it will run to the center of it's map and stay there in the ideal efficiency island the entire time. This would be good for 1-mile or 10-mile or boat constant WOT racing because the turbo outlet temp will be minimalized at the cost of using a heavy wheel. However in drag racing we have all the tricks, 2-steps, transbrake, nitrous, which make spooling instant or fast as we want, So there is no issue using a too large turbo in that case. You wouldn't want to try those things on a normal street, though. Generally speaking. It isn't desirable to have to use nitrous everytime you leave a stoplight just to move the huge wheel.


I'm not really sure what you say here, I'm trying to figure out how you are thinking so I can provide suitable comparisons. It is very simply stated like this:
1. For daily drivers we push the compressor off the map to the right to minimize wheel mass. This makes for good cold start performance and rapid response. It can lead to EGT issues and power limiting at high temperatures so quality fuel and water injection play a large role in sustained performance at high output, like constant WOT with a small turbo, we can bring the EGT down using alcohol and water and keep going that way. Otherwise the EGT will begin to push too high after a while and limit us and possibly damage the engine using such a small turbo. It depends on the type of racing, right? If the event is 1/4 mile you can get away without too much trouble running off the map. IF you are 1-mile it will need some help if the turbo is very tiny. If its some kind of rally or long duration event then maybe the turbo isn't constantly being pushed to the very edge of it's map for long durations.

2. For drag racing where nitrous, 2-step, CO2, T-brake, etc... is used the turbo should be sized 30-50% larger than the power it needs so the efficiency will peak and stay center island the entire time, this is especially important for constant WOT boat applications and long duration racing similar.