Interesting stuff, thanks for the post.

 

It's what @MatthewMiller has been saying all along.

 

does this affect fuel economy? like if u shifted just past peak torque on a road track, would you burn less fuel than an LT5 that is shifting up at 6900?

 

Just taking a WAG but... most vehicles I've seen, be it turbo 4s V8 what have you... similar power equates to similar fuel consumption because its physics. You require X to produce Y. Given the LT5 is capable of higher horsepower I would surmise that there is greater fuel consumption banging the red line on it vs a box stock l98. Equal power however I would say they burn the same amount of fuel even though rpms are drastically different...

I would say no... although there are stipulations and testing that can be done to be sure. Either way you're burning a crap ton of fuel in both on a track.

 

IMO, same hp and size, less RPM = less fuel consumption b/c less friction/heat.

 

also true... my experience is with the eco boost towing vs 5.0ls and the eco boost was actually noticably worse. But that's in the extreme... if you're running at a much higher VE I suppose that could offset the friction difference however. We should test it. It's not 100% fair as the lt5 uses those trick nikasil liners in the cylinders so that's a decent chunk of friction removed from the equation... I don't know lol.

Again, I really don't care... I doubled the power in my car more or less, (hopefully) beat the snot out of it way more and only took a 1-2 mpg hit in straight town driving. But looking at my VE tables before and after the engine work it would appear that fueling under 2200 rpm (in town speeds at steady state) is pretty close to the same so I'd guess that would mean it makes similar power at those speeds??? I don't know. Wrong type of engineer. I'll make my own fuel though lol.

 

The videos that he has done with that 4.3 have been pretty interesting. The dyno run of my 85 reflect pretty similar power and torque RPM peaks, even with boost. Mine may be slightly higher as the runners and plenum are siamesed: 5,300 for the horsepower and 3,500 for the torque peaks.
I have been seriously considering switching from my TPI setup to a Miniram for a while now.

It would be interesting to see a dyno run of that T Ram that you found for your kart.

 

He did a tpi shoot out and ran a T-ram and siamesed runners... and extrude honed... and others lol.

 

thanks for posting that vid tom. and i think it was @ghoastrider who posted one of his earlier. as a street car i think the tpi is perfect. huge torque. dont need top end. and come on when the manifold, and intake components are cleaned up with the eagle 1 aluminum cleaner, it looks super cool.

frankly i think the t ram (which was new to me until tom posted it up) the super ram and the tpi, and most of all, the LT5, are my fav fuel injection intakes of all time. while i love the performance increases of the mini/lt1/ls1 with the plastic covers i just find them meh.

 

I must have missed the T-ram one. Now I'll have to find that video.

 

It was on a 383 but results are similar.

 

Yes, there is the governing factor of X to Y as mentioned. You need a certain mass of fuel to release a certain amount of energy when burned.
However, engine efficiency is the key component here - Lighter internals and a roller valve train for example will allow the same power/torque at the crank from the same displacement engine (all other items equal) when compared to another one due to less internal losses to make combustion occur while consuming the same fuel. Then other items to consider are less drive train losses or less parasitic losses in the accessories when getting power to the wheels. The less losses you have is more energy released from the fuel turning in to motive force at the wheels. So, you either go faster or save a bit of fuel.

 

As soon as the snow melts....I'll do it. I believe that it is the most powerful intake on a stock or stockish 350....but we'll see.

 

I have a few thoughts:
Would you please tell my wife that I can, on occasion, be right? She needs to know. Really.

That's an interesting video. What we do see on the small engine is that the dropoff of the torque curve isn't as severe, and I think that's literally a function of the smaller displacement demanding less air than the large engine does. So the torque peak is in the same place, but the power production holds up a little better above that peak than it does on the large engines. But in all these engines, we see a falling torque curve and a near flat power curve for quite a range of RPM. What that's telling you is that the intake is strangling the engine of air due to the antiphase resonance (that was in-phase around the torque peak). With a sane intake, that power curve would keep rising instead of holding flat. This is not the way to go fast.

The torque peak isn't determined solely by the intake, of course. The cam and a bunch of other parameters still have a say. A dead-stock L98 makes peak torque lower than 4000rpm. So just because the engine peaks at 4000rpm, that doesn't mean the intake's resonance peaked at that RPM. It's probably lower than that, but someone will have to do the math and accurately measure the full intake tract to get an idea of what it exactly is. Not that even the "stock" LB9 had long-tube headers and a bunch of intake restrictions removed.

In the 383 chart, I actually think the small uptick above 6000rpm is not an anomaly. I think the engine has moved past the nadir of the antiphase resonance and is starting to head back toward in-phase resonance. Resonance is period, and has "orders" that are multiples of the fundamental resonance frequency. Also, the intake is going to have an RPM at which its resonance is perfectly in phase with the intake valve (where it boosts cylinder pressure and power) and it will have an RPM at which the resonance is perfectly out of phase with the valve (where it's killing cylinder pressure and power). I believe the antiphase RPM should be 50% higher than the in-phase RPM. In between, it's either getting more in phase or more antiphase. So if the TPI intake's in-phase RPM is 4000rpm (just to use easy numbers), then it's anti-phase RPM is 6000rpm. But it will have a second-order in-phase RPM again of 8000rpm. So when their 383 reached past 6000rpm, I think he was seeing the intake resonance becoming less antiphase and that might account for the little uptick in torque and power.

It's true that every intake has a resonant RPM, but that doesn't mean the engine is ever going to see it. The LT1/4/Miniram runners are so short that it's probably "tuned" for something like 10,000rpm. The idea was create an intake that was neutral to power production because the engine would never approach its resonant frequency. This gave the benefit of allowing a higher compression ratio because the cylinder pressures would stay more linear. It's a better way to build an engine: "supercharging" a piston engine at just one RPM means you aren't effectively getting the best BMEP at other RPMs. The newer LS and LT engines have longer runners that probably resonate roughly at redline. This makes sense because cylinder pressure are naturally already falling by then, so maybe those intakes can bump the beyond-peak torque up a little without risking detonation (plus newer engines have much better control of fuel and spark parameters).

RE torque peaks and efficiency: yes, running an engine at peak torque is usually the most efficient RPM for it in terms of brake specific horsepower (power per unit of fuel burned). But don't forget that all these dyno curves are generated at WOT. The torque peak is much, much lower as you let off the gas pedal. That's why cars get better mileage when lugged down to 1500rpm or less on the highway, where you barely have the throttle cracked open and the car's power demand to hold a steady speed is very low.

Other things besides power output can seriously affect fuel economy. Compression ratio is a biggie. So is combustion chamber design and volume (which is also related to CR). There is a ton of variables. Consider that modern F1 engines are currently getting around 50% efficiency in converting their gasoline to power at the crankshaft, whereas our C4 engines probably struggle to get 25% efficiency (this and BSFC are not dependent on power numbers, so they are directly comparable). But for any Gen1 or 2 small-block Chevy, they are a lot more alike than different and so BSFC is probably pretty similar, regardless of the parts thrown at it.

 

Indeed. Stock tq peak is around, 3200 RPM.


I agree....the 4th harmonic.



That's exactly right. I did the math once and it came out to ~9000 RPM.

 

I actually stopped at TPIS earlier today as they are less than 1/4 mile from a vendor we use for work and spoke to Jim about switching from my current setup (ported and siamesed SLP runners and plenum, Edelbrock high Flow base) to a Miniram. Talked a minute about the video and the effect the runner length has on the shape of the power curve.
I'll be switching to the Miniram in the future.

 

That sounds like it might have been an interesting conversation..


...and I meant to comment on this earlier:
Sure! I'll tell her! That'll work!