Finally! A valid TFS-R and TFS Box R intake dyno comparison on a street stroker.

[FastDriver]

I’ve finally found a valid comparison and it turns out that the common belief is is wrong. In fact, the TFS Box R is the better set up for a street-oriented 302-based stroker combo. I’ve really wondered about this for a long time, and have always thought about swapping my box upper for a standard TFS-R upper.

Hopefully, this will help someone out there that tries to do the research prior building their combos.

From “Dyno-proven Small-block Ford Performance”:

Before getting to this test, I have to admit not being a big fan of these so-called box upper intakes. Testing in the past, both for my previous 5.0L book and a great many magazine articles, has revealed the lack of runner length to be terribly ineffective for the vast majority of street applications, including supercharged and turbocharged engines. This test demonstrated the importance of keeping an open mind and continuing to test. The 331 test engine consisted of a Coast High performance stroker assembly with a 4.030-inch bore, a 3.25-inch stroke, and a set of forged connecting rods. The 331 was further equipped with an XE274HR cam, providing a .555/.565 lift split, a 224/232 duration split at .050”, and a 112-degree lobe separation. This cam has proven effective for a great many street-oriented 5.0L-based buildups. Both TFS upper intakes were fed by a 75 mm Holley throttlebody and matching EGR spacer, while the fuel was supplied by a set of 36lb injectors. The engine was also equipped with an MSD distributor, a set of Hooker headers, and the FAST management system. The heads were CNC ported 185cc TFS Twisted Wedge Heads.

While I was hard pressed to recommend a box upper intake for anything but a high-rpm or possibly a large-displacement stroker combination, the new TFS Box R upper had something going for it that the other designs did not, namely increased runner length. Unlike early attempts, the TFS Box R upper intake featured extended runners into the common plenum. It is this extra runner length, combined with a straight shot from the upper through the effective lower and into the head port, that helps produce an effective power curve. Swapping in the new Box R upper intake in place of the TFS R upper intake resulted in a significant jump in power, from 415hp to 441 hp. Even more impressive, given the box design, was the fact that the increase in power from 4800 rpm to 6,000 rpm cost little to no power elsewhere in the rev range. There was a slight drop in power, roughly 4 ft-lbs, at 3700 rpm, but this was offset by a gain of the same amount at 3200rpm. Unlike the previous testing on these box-style upper intakes, the TFS version offered impressive power gains from below 4000 rpm without any low-speed penalty. That it looks cool and fits over raised valvecovers is just icing on the cake.

From Caption one, a picture showing the upper intake dismantled:

“A peek inside the Box R upper intake reveals the short runners and radiused port entries. This design also lends itself to porting to further improve air flow.

From Caption two, a picture showing the Box R upper side by side with the standard TFS-R upper:

“Both TFS intakes relied on the same lower manifold. The difference in runner length between the two designs is evident in this photo. The TFS R (right) offered longer runners while the Box R offered shorter runners and increased plenum volume.

From Caption three, a dyno graph comparing the horsepower curves from 3000 rpm to 6000 rpm:

“Obviously the Box R upper intake was the clear choice for this 331 stroker engine. Though the power gains posted by the Box R were most prevalent past 4500 rpm, the gains came with little or no tradeoff in power below that point.

From Caption four, a dyno graph comparing the torque curves:

“With the exception of a minor drop at 3,700 rpm, the Box R upper intake bettered the TFS R upper intake from 3000 to 6000 rpm. Note the huge torque gains between 5,000 and 5,500 rpm. Torque production with the Box R upper intake was up by as much as 21 ft-lbs at 5,200 rpm.

Now, the following dyno comparison test in this book makes the Box R’s advantage even more clear. On the same motor with the box upper, a 75mm TB is swapped with a 90mm TB and yields a max of a 14hp gain at 5800 rpm and 12 ft-lbs at 5600 rpm. I don’t think the standard TFS-R upper will even accept a 90mm TB. Peak power jumps from 441 to 454 hp on this motor. I think this number would be the more valid comparison to the standard upper.

So in conclusion, the difference of 39 peak hp (415 vs. 454) without any loss in low end TQ on a 331W with otherwise very street-oriented parts dispels the myth/conventional wisdom that Box intakes are only for high revving strokers. Additionally, based on the author’s experience, the common belief that Box intakes are somehow advantageous to their counterparts in boosted applications is also false.

If this surprised you, be honest It surprised me. Frankly, I expected the Box to come out on top at peak, but also expected it to suffer in low and midrange power, whereas it matched on the low, and outmatched even in mid-range. Thoughts?

 

[90lxcoupe]

It dosent suprise me at all, FWIW, i didnt notice much difference one way or the other when i put the box intake on my car on the street. I wish i had some solid back to back track passes with the two.

People have been telling me that the intake is too big for my car since i installed it

 

[FastDriver]

So you don't really know what you gained or lossed or how the powerband was affected?

 

[tmoss]

The test used the same cam, so the box was better for that cam. Change the cam specs to favor a long runner intake and use the long runner upper and you might get a flip flop again.

 

[NIKwoaC]

This test demonstrated the importance of keeping an open mind and continuing to test.

DING DING DING! Winnar!

On the same motor with the box upper, a 75mm TB is swapped with a 90mm TB and yields a max of a 14hp gain at 5800 rpm and 12 ft-lbs at 5600 rpm. I don’t think the standard TFS-R upper will even accept a 90mm TB.

There are two versions of the long-runner R, one that is EGR friendly and has a 75mm opening, and one that does not have any provisions for EGR but does have a 90mm opening. Mine is the latter.

SO, swapping from a 75mm TB to a 90 provided SIGNIFICANT power gains UNDER 6000 RPM on a mild 331? Hmmmm, what does that say for all those stubborn hillbillies with their ricer CFM math that say a 75mm TB is "enough"? What does that say for that useless throttle body flow data and "required CFM" per engine size garbage that people like to throw around on the internet?

Chris, I need a scanned image of that article to shove in the face of the next guy I see that says a 75mm TB is "enough" for a 408. LOL!

Even after all this, I bet there are some who will say "yea, but, but, but, I bet it would suck to drive on the street. I bet that 90mm TB would cause all sorts of drivability issues."

I love stuff like this! So, who wants to buy my long runner R upper? It's for sale. Cheap.

The test used the same cam, so the box was better for that cam. Change the cam specs to favor a pong runner intake and use the long runner upper and you might get a flip flop again.

Fair point! BUT, the question is; would the cam for the long runner be more or less aggressive? Drivability?

 

[ViperPunk]

interesting read! good find bro!

 

[FastDriver]

The test used the same cam, so the box was better for that cam. Change the cam specs to favor a long runner intake and use the long runner upper and you might get a flip flop again.

Hi Tom! Glad to have someone with your experience here to discuss. I thought that the XE274 was a very popular grind for street 302-347s, including fuel injected long-runnered combos.

I agree with you in premise. It's only one test. Though, this is the only documented comparison test with the Box-R upper that I've seen to date. Have you done any testing? Do you have any experience with this particular boxed intake?

This upper has longer runners than any other boxed intakes I've seen since they extend up into the plenum. Do you feel this particular box would be surpassed by the others on the top end, and if so, around what RPM shift points should users look to swap to them?

There are two versions of the long-runner R, one that is EGR friendly and has a 75mm opening, and one that does not have any provisions for EGR but does have a 90mm opening. Mine is the latter.

Nik, what took you so long? I knew you'd like the article.

And, thanks. I thought the long-runner uppers were all 75mm.

SO, swapping from a 75mm TB to a 90 provided SIGNIFICANT power gains UNDER 6000 RPM on a mild 331?

Yep. Again, the hp & tq peak differences were at 5800 and 5600, respectively.

Hmmmm, what does that say for all those stubborn hillbillies with their ricer CFM math that say a 75mm TB is "enough"? What does that say for that useless throttle body flow data and "required CFM" per engine size garbage that people like to throw around on the internet?

I would've been one of those guys telling you that about a 75mm vs. a 90mm. In fact, I think I have said that to you in the past. I wouldn't have expected that result.

From that article, here's how I gather you could tell if it will make a difference in your motor. In the article, they recorded a vacuum of 1" at WOT. Switching to the 90mm TB resulted in a drop from 1" to .3" vacuum @ WOT. I'm assuming they were taking these measurements at high rpm. I would also assume that you'd need a combo where the heads and intake were not already the weak point in flow. Both of those assumptions should be evident if you measured your manifold vacuum, particularly if you can figure out how to datalog that info. Of course, keep in mind that a vacuum doesn't necessarily indicate that the TB is the cause - could be the MAF, filter, piping, etc...

On the dyno graph comparison, there was no hit to torque or power anywhere. The difference increased almost linearly as rpm increased. I would have expected the 75mm to start reaching its potential before the 90 mm actually made any difference. From this test, that does not seem to be the case.

Chris, I need a scanned image of that article to shove in the face of the next guy I see that says a 75mm TB is "enough" for a 408. LOL!

I can't scan it for you, because I downloaded the digital book for $25. I think we can work out something better, though. Shoot me an email to [email protected]

Even after all this, I bet there are some who will say "yea, but, but, but, I bet it would suck to drive on the street. I bet that 90mm TB would cause all sorts of drivability issues."

I wouldn't expect drivability issues, but the tune would have to be more precise, since opening the TB blade by any given angle will result a greater difference in the amount of air that flows. To be more concise, you lose resolution regarding the TPS input at low throttle. Naturally, I'd expect a motor with a huge TB to be more sensitive to the throttle down low. So that means 1/3 throttle with the small TB might be more like 1/4 throttle with the larger one. At low RPM - cruising speeds, you might not feel a difference in acceleration between 1/3 throttle and WOT.

Even in this test, at 3000 RPM, full throttle with one wasn't any different than the other.

I love stuff like this! So, who wants to buy my long runner R upper? It's for sale. Cheap.

Until we see more testing, I'd hold on to it to verify that the Box actually does make more power on your combo.

Nik, if I head that way in the next year like we talked about (a big if) and you haven't swapped it, let's get together and do a little dyno testing, for the hell of it. I'm running a 75mm TB on my box upper, because the HP kit's piping is too small for a 90mm - that's what I was told. I have higher priorities to work through at the moment regarding both life and the car, but eventually, I'll fab up larger piping and switch over to the 90mm TB.

Chris

 

[tmoss]

Hi Tom! Glad to have someone with your experience here to discuss. I thought that the XE274 was a very popular grind for street 302-347s, including fuel injected long-runnered combos.

I agree with you in premise. It's only one test. Though, this is the only documented comparison test with the Box-R upper that I've seen to date. Have you done any testing? Do you have any experience with this particular boxed intake?

This upper has longer runners than any other boxed intakes I've seen since they extend up into the plenum. Do you feel this particular box would be surpassed by the others on the top end, and if so, around what RPM shift points should users look to swap to them?
Chris

The R box and Vortec box are the best I have seen. The others don't come close. I have not done testing on them but my customers have. And, has been pointed out, on a 408 using a 75mm long runner upper with s shorter duration cam and then switching to a 90mm box and then saying the box is better is not the best comparison.

 

[FastDriver]

And, has been pointed out, on a 408 using a 75mm long runner upper with s shorter duration cam and then switching to a 90mm box and then saying the box is better is not the best comparison.

You got me scratching my head on this one, bud. The article I posted compared the same 331 and both had a 75mm TB. Are you referring to another comparison?

 

[Ratchet27]

Makes me want to sell my upper and get the boxed version.

 

[tmoss]

You got me scratching my head on this one, bud. The article I posted compared the same 331 and both had a 75mm TB. Are you referring to another comparison?

forgot that due to the 90mm chat I guess, if a 75 is compared to a 75 that takes one variable out of it.

 

[Ratchet27]

I'm really thinking about making the switch but I'm thinking the box upper will not clear my hood. I'm already rubbing a tad bit with a 1.5inch cowl and dont want to get another hood. I do have drop motor mounts. I looked on TF's website and I'm pretty certain the box upper is actually an 1 inch or 1.5 inches taller than the regular TFS R upper. Does anyone have first hand experience with the box upper? Is it taller than the regular R upper? I just had it in my mind that the box upper would be a bit shorter.

 

[90lxcoupe]

So you don't really know what you gained or lossed or how the powerband was affected?

No not really, when i changed just the intake i never got a clean pass on the car and i also swapped to 4.30 gears around the same time. Its also very hard to tell a few hp one way or the other on the street unless im in 4th gear in my car, and that means im in the neighborhood of 100mph, which isnt very smart. The car dosent hook till 3rd on the street so its hard to get a real gauge on it.

Now i also have a custom cam in the car and bigger headers. Dez Racing is having a dyno day on 10/30 so i will have solid number of how much more RPM and peak power it will make(same dyno usedlast time). My car isnt a good example because i have been swapping parts since i put it together. I am hoping that is going to stop for a while and i can just run it and have a strong base to compare from.

 

[FastDriver]

Cool man, I look forward to hearing the results.

Ratchet, everything I've read says that it is substantially taller than the standard TFS-R upper. Most say you need a 3" cowl hood to clear it. I'm running a 2.5" cowl with a UPR K-member, and the motor sits a bit lower. It clears the hood just fine.

 

[90lxcoupe]

You need a 4" cowl hood to clear a stock box R, there are tricks you can do to lower them but it is a ton of work and will cost you a few bucks at the machine shop

 

[Ratchet27]

Ok. Guess that puts that idea out the window. Thanks for the replies guys.

 

[5spd GT]

Interesting test, but I have to agree with Tom. The camshaft is the gatekeeper to all incoming and exiting air. The particular combination switch (intake) could be tailored towards one side or the other. Atleast that test is much better than many comparisons I have seen. A 75mm TB is plenty for that combination IMO.

 

[5spd GT]

SO, swapping from a 75mm TB to a 90 provided SIGNIFICANT power gains UNDER 6000 RPM on a mild 331?

The only difference between those two intakes tested is the TB opening diameter? The runner shape, length, taper, etc. is all the same?

 

[FastDriver]

It feels like that's a bit of a hand-waved answer. Why wouldn't these supposed advantages of long-runners manifest themselves in that range with any cam?

How do you take advantage of a long runner intake? Cam it to make power in that powerband. Correct me if I'm wrong, but the XE274 is pretty well documented and should be a pretty tame cam on a 331 with plenty of vacuum and pretty streetable. It should produce plenty of low-mid range tq. It's also not going to want to rev out above 6k, which IMO doesn't take full advantage of the shorter runners in the Box-R. I think the Box-R would prefer to have an extended rev-range well into the mid 7k range, perhaps higher. So to me, it seems like this cam should be advantageous to the long-runner intake in this test, if anything.

Still, until I've seen otherwise, this article has shown me that the commonly held perception that boxes will trade low and mid-range power for high-end is a myth. Perhaps it applies to other designs, but it surely doesn't seem to apply in this test. Again, I welcome anyone to demonstrate their point with a different comparison between this box upper and a standard TFS upper.

The only difference between those two intakes tested is the TB opening diameter? The runner shape, length, taper, etc. is all the same?

Not sure why you quoted his question to me. The test he was asking about, and the one you appear to be asking about now, are of the same motor from bottom to top, with the exception of a swap from a 75mm TB to a 90mm TB on the same TFS Box-R upper manifold. The TB swap resulted in 14 extra hp below 6000 rpm.

 

[FastDriver]

Here's a dyno of the following combination:

331, AFR 185s, with an RPM II long-runner intake and the XE274HR cam:

As you can see, this thing has a nice broad tq curve peaking at around 4500 and falls off over 6k. HP is peaking around 5600 RPM which should make for a 6000-6200 shift point... IMO a well-matched cam to that RPMII intake.