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Its been a while since I posted anything here about my car (its been 2 years!) . This is largely because its been pretty boring with the car, it works, is reliable and does what I need it do every day. The car hasnt changed much in its mechanical config, its pretty much the same engine package I had in 2016 when I first posted on here. However about 6 months ago, I was surfing YouTube when I came across a video from Richard Holdener, who (as he always does) was running back to back dyno runs to test parts, configurations and outputs. In this video he was comparing a TFS R and TFS Box R upper on a Ford 331 engine. I took interest in the video as the engine in question had very similar specs to my engine (331, TFS 185 head, XE274 cam). What was uncovered was that the 331 test engine dialled in at 416 HP with the TFS R long runner intake and 454 hp with the TFS Box R intake. With the only change being the upper intake..Wow thats a lot I thought !!? Now I normally am very sceptical of internet dyno tests and their quoted horsepower figures, but Richard Holdener does have some credibility, so this sparked my interest. The seminal question was …Is there really almost 40hp in an upper manifold swap ? And Could I get that 40 hp from my Miata’s 331 ?
Background from 2016: ABuilkd sheet form 2016:
Std block 331 (3.25 stroke and 5.4 in rods) (Forged Mahle pistons, SCAT 9000 crank and SCAT I beam rods, ARP hardware on mains and rods ) 10.75:1 TFS 11R 190 heads (56cc) – (296cfm intake flow @ 0.6in) TFS R long runner intake 85mm Accufab Throttle body 90mm Ford Lightning MAF with 39lb/hr injectors 90mm silicon intake tubing (K&N filter)
Ed Curtis Cam 222deg@50 intake duration and 0.6 in lift 1.72 TFS roller rockers EECV ECU (wasted spark twin coil towers) with MSD DIS 4 ignition unit.
The engine spec (my own design) was for a daily driven car that could deliver good performance in the Miata. The result I obtained was a best power output of 248 rwkw (335rwhp) on a Mainline dyno. The engine was loaded with Air con, power steering, mechanical water pump etc and was pulling 1.5 inches of vacuum at full throttle (indicating a slight restriction). But it was a decent result that I was somewhat satisfied with at the time. But I had always wondered if I could have improved on the combination. After that I had installed some emissions based catalytic converters on the car to help with the fuel smells, after this the cars power dropped to 242rwkw or 324rwhp. That was 2016...
Get data, good data - for Information is key to success:
So from the first view of the Richard Holdener video, I then started my journey to unlock everything that I could about the TFS Box R. Was it any good ? Were people using it in daily driven applications? Could it fit under the hood ? What did it really flow ??? I had a lot of questions but the answers to them were not so easy to track down. But I was able to find many answers on the forums.
From my research I was able to essence my data collection adventures led me to the following info:
TFS Box R is 12.25 inches tall (thanks SLO 5-OH) form bottom of lower to top of upper (Wow that’s tall!)
TFS Box R upper flows approx. 295 cfm on average across all runners (Good!) (Thanks TMoss)
TFS Box R has proved to be a strong performer with a lot of potential for more (Thanks Ed Curtis)
TFS Box R has approx. 9 inches of runner length
TFS Box R weight 19.5lbs
TFS R Long runner upper flows approx. 265 cfm on average
TFS R long runner has inconsistent cross-sectional areas along the length of its intake runners (Thanks SuperIrish for providing a cross sectional pic, it was very eye opening)
TFS Long runner is 11 inches in height from bottom of lower to top of upper
TFS R Long runner has approx. 12 inches of runner length
TFS R Long Runner weight 16.5lbs
TFS 11R head has approx. 3.75 in of port length from valve to intake flange
TFS R Lower intake flow is approx. 320-330cfm
Data Analysis Phase
With my trusted Dynomation 6 wave tuning software that I have been using for 30 years and the data in hand on the TFS R and TFS Box R, a picture was beginning to emerge of why my engine was only good for 324rwhp. The simulation correctly showed that my heads were being limited by the flow rate of the upper intake. The overall tuning length of the intake runners didnt seem to make much of a difference but the flow rate increase most definitely did. The performance attributes were as follows:
The TFS R long runner tops out at 265cfm whereas the TFS Box R will flow to 295 cfm on the intake. That is an increase of about 11%.
The TFS 11R head I have was good for 296 cfm.
The TFS R long runner intake was limiting my 190 11R heads intake flow to 265cfm (and limiting my power output)
TFS Lower intake was good for 320-330cfm of flow (no restriction here)
The tuning length of the TFS R long runner (head tract + intake runner tract) was 15.75 inches (valve to plenum opening)
The tuning length of the TFS Box R (head tract + intake runner tract) was 12.75 inches (valve to plenum opening)
Dynomation 6 wave tuning had shown that at 6500-6800 rpm (my rpm limit) the intake tuning pressure wave arrives perfectly on the 3rd harmonic when using a 12-inch inlet tract length. In essence the intake pressure wave is coming into the inlet tract at full pressure and at the right time around IVO (good!).
In summary the TFS R long runner was limiting flow, was too long in its runner length for optimal power production on my 331 and it had a design issue with its cross-sectional areas not being consistent throughout the length of the port, across all its port layouts.
In essence the TFS R long runner upper intake is a P.O.S.
Decision: Always follow where the data takes you
This was easy….all the data was telling me that I needed to ditch the TFS R long runner and get a TFS Box R. From what I could see the uplift in flow would be accompanied by a similar uplift in power. So, I could see from the Dynomation 6 modelling that the engine would produce approx. 270 rwkw with the TFS Box R. Optimistic ? Maybe, but worth a shot for sure!
So, it was a green light from me. I bought a TFS Box R Upper in black from Summit and whilst it was being shipped, I had to work a few things out…a new problem arose.
My new problem: How to get that THING to fit under a V8 Miata hood ?
The TFS Box R is tall, real tall. AT 12.25 inches there no way it will fit under any stock hood every created let along a Miata hood with a V8 under it. The TFS R long runner I had fitted to the car would fit under the hood. It was 11 inches tall, so I needed to get the TFS R Box to match that height..not easy..but doable I thought!
The TFS Box R upper is a two-piece design it has the cast runner section and a ‘adapter plate” that bolts to the upper and then allows it to be bolted to the lower. This adapter is over an inch tall. Thankfully BLUE351 had come across this in the past and had tooled up to produce thinner spacer plates that would reduce the approx. 1-inch-thick spacer to just 3/16 in. So I ordered one from BLUE351 at Corral.net, they are of impeccable finish and quality and came with all the right hardware to fit it (shorter studs and hex countersunk screws).
But that wasn’t enough. I needed another 3/8 of an inch to hit my target of 11 inches. When I finally received my TFS box R upper I had just shy of 3/8 in machined off the bottom. This got me to my 11-inch height but brought other issues. There was more work that needed to be done around the mounting bolt areas. I needed to use a die grinder to cut a deeper relief into the upper intake for mounting studs to clear and for a ring spanner to fit over the mounting nut.
Also, as I cut so much off the upper, I needed to get my die grinder and blend the lower ports to be lined up with the mounting flange openings on the thinner intake spacer. I simply bolted them together and used the die grinder to blend the ports to match the spacer port openings, it was just some mild blending, but it needed to be done for a neat finish.
I assembled the new 3/16 adapter plate to the upper without a gasket and just using silicone sealant between the mounting surfaces. This was the cleanest way to do it.
So, my upper was now complete and after checking the heights with a mock up model of the TFS Box R and Play Doh in the car, I could confirm that it was going to fit ! (With ¼ inch to spare..phew!!)
However, the reduction in height has removed more from the TFS Box R inlet tuned length tract and its now sitting at 11.61in. I took about 1.15 inches of height out of the intake. So, my runner length is shorter than the standard Box R length of 12.75 inches. But I am still close to the 12-inch ideal as predicted by Dynomation.
Will I lose torque because the runner length is now “too” short ?? Unlikely..because it is so close to what Dynomation predicted the ideal should be at around 12 inches.
Ok so there is just no way my standard fuel rail was going to fit now. The TFS Box R has been lowered so much that the fuel pressure regulator now fouls on the upper and it won’t seat on the lower intake with the fuel rail installed…that’s a problem, but how to fix it?
Aftermarket fuel rails ? Trickflow or Aeromotive ? Sure…but they are expensive and from a packaging perspective all the extra braided lines, external regulator etc, take up a lot of room under the hood and in the Miata engine bay its already quite “cosy”…
Do I really need aftermarket fuel rails? From a capacity perspective no, the standard rails will be Ok for around 450 hp which is where I am aiming at.
So, in the end I simply modified the standard rail but cutting off the return line with the regulator flange and rotating it 45 degrees, so the regulator cleared the upper. Some silver soldering later and it was leak free and ready to rock! I use the standard Motorcraft factory regulator, no need for any adjustable unit as I will use the SCT X3 Flash tuner to modify the fuelling. Factory rail pressure is approx. 43psi. And the factory regulator is very compact and reliable.
After all the other gremlins, Fitting the TFS Box R upper and my modified factory fuel rail setup was relatively easy, and everything lined up perfectly first go.
The car started instantly, and the dyno session was booked for the following day!
Judgement Day – On the Dyno
When I drove the car around before the tune, I noticed some things straight away:
Idle was very smooth but slightly rougher, like it had a slightly lumpier cam in it. I liked it �� Immediately I noticed the car felt “lighter”, the engine picked up speed quicker I noticed that the car at the slightest throttle angle increase speed and would want to keep adding speed even without extra throttle There was “maybe” a slight decrease in torque below 1250rpm Car would cruise in 5th at 900rpm and with a slight squeeze on throttle it would pick up speed There was Definitely a solid increase in torque and power above 3000rpm The car was running so much more effortlessly on the freeway, much less throttle needed to go uphill or pass another car. This intake was FLEXIBLE and had a great SPREAD of power. I could easily cruise in 5th with 1000rpm on the tacho and squeeze the throttle and accelerate with ease, just like I could before with the TFS R long runner but better, much better!
At the dyno, we were all keen to see the results. The upper intake was the ONLY change to the car since the last run. It was identical in configuration. After a couple of light throttle runs to setup the new fuel and timing curves, the car returned a result of 267 rwkw (358rwhp) at 6700 rpm under full power, with the curve still climbing. We did not want to push it any harder.
This was a change of 25rwkw (267rwkw-242rwkw) or 33.5rwhp. This equals about 40.4hp at the engine’s flywheel (This Mainline Dyno has a 20.5% power drop through the drivetrain).
I will repeat that result again a 40.4HP INCREASE at the flywheel by removing the TFS R long runner upper and replacing it with the TFS Box R Upper.
This result mirrors the Richard Holdener result almost exactly.
To say that I am happy with the result is an understatement. This intake has really woken up the engine both from a response and a performance perspective. I could not find any aspect of driving that has been hurt by the TFS Box R. Cold Start is identical, light throttle is better part throttle is better, top end is better, mid-range is better. The ONLY area that seems slightly and it’s really only slightly worse off is sub 1250 rpm, but its so slight you could easily miss it and say it’s on par with the TFS R Long runner.
Conclusion
The TFS Box R is a great intake that is definitely suitable for street driven cars and is not just a “race” intake. It has great flexibility and range to behave perfectly for daily duties as well as performance duties
My performance improvements came about because it was the upper intake that was causing the restriction in my engine (remember my original 1.5 Inch vacuum at full throttle) . My TFS 11R heads could flow 296cfm, my TFS Lower could flow 320-330cfm and the TFS Long runner Upper was only flowing 265cfm. The 85mm Throttle body and 90mm MAF could supply enough cfm to feed the heads their full 296cfm, which left only the TFS Long runner upper as the restriction.
By installing the TFS Box R I essentially removed this restriction and allowed the heads to ingest to their full capacity of 296cfm. Hence the power went up by a ratio that was in line with the increase in airflow.
If I had TFS 11R 170 heads that flowed only 260cfm I would not have seen any benefit from the TFS Box R intake swap. So, it’s important to understand the flow of the entire inlet tract from air filter to valve. Your engine will always be limited by the weakest flow link in that chain.
There is more power to be had from the combination, but I will now need to increase my cam’s aggressiveness. I have a new Ed Curtis cam to put in it one day its on my garage shelf. Its 234@50 and 0.6in of lift. It could provide another 10-20rwkw (13-27 rwhp). This will take the engine to up to around 283 rwkw or 384 rwhp. A very good number for any engine of this type.
Another option to add for more power is to port the TFS Box R to 320-330cfm (as per Ed Curtis porting) and go with a TFS 11R 205 head with 321cfm of flow. This would yield another 8% more power.
Or I could do the heads, Box porting and cam..but thats a lot of work and $$!!
I find the TFS Box R looks a lot better too !
I hope that helps anyone out there looking to make the move. I am glad I did it !
OK...its been a while since I last posted and as it seems quiet on these forums lately I thought I would put some stuff in.
1) I have decided to pull out my engine to refresh it and do some upgrades (cam change)
2) I will be upgrading to a TKX transmission as I am now at a point where the T5 is on the limit of being reliable. I want a more solid style of transmission and the TKX is likely twice the strength of the T5z.
So I will update all with some pictures when the time comes to do it...
I'll look forward to the updates!
Looks like you are running the Explorer accessory drive?? I wasn't sure the alternator would fit under the hood, but it doesn't look like you've had any problem.
Thanks for all the detail in your posts!
Bryan
Yes the Explorer accessory brackets fit just fine under the hood. The air con compressor was too close to the frame rail so I notched it slightly to get the clearance. I like the explorer setup much better, Its pretty solid the bracketry all round, and its dirt cheap.
Very good to know, thanks. I've gone the Thunderbird route - 1992. It had the PS bracket, which I am retaining (I won't need the AC side of the bracket), but it was missing the alternator bracket. I'm going to piece something together myself for that. Comparing the SN95 Mustang / Thunderbird and Explorer accessory brackets, I would not have expected the Explorer to clear (either alternator or PS pump), so this is very good to know.
I'm currently working on modifying the oil pan for clearance, then it is back to the accessory drive.
08-12-2022, 08:58 PM
Some Updates that might be of interest..
