TR6 Opinions: best way to get 150hp TR6?

[TR3driver]

Kas always claimed he could get more power with ZS carbs, but he may have been somewhat biased. OTOH I have yet to hear of anyone that reported a significant power loss when switching away from Webers, so maybe Kas was right.

On the way to Breckenridge via Hoosier Pass in 2001, I noticed a buddy's TR3A blowing black smoke, even though he stopped twice to change jets in his DCOEs. I drove right to the top with my SUs, no black smoke (though it was running a little rich). Afterwards I touched up the mixture a bit with a simple turn of a nut with my fingers. No worries about spilling $60 jets all over the ground.

For some odd reason, my DCOEs are still hanging on the garage wall

 

[Darrell_Walker]

If it was me, and I wasn't going to do the supercharger, I might look at the European petrol injection system.

 

[TonyPanchot]

I have RG trip / 1:55 rockers / shaved head and r 2 cam
45xxx original on the motor / od too / runs wicked fast
\ don't forget to consider suspension upgrades to handle the power

 

[3798j]

For some odd reason, my DCOEs are still hanging on the garage wall

I've enjoyed mine for years now as "shelf art". Could never reach a good level of compromise (for me). While I was able to have the best of idles, it was either a flat spot on "tip in" and good gas mileage, or running great with spark plugs way too wet. When the TR4A ran best with them, it was always too, too rich. Going back to the Zenith Strombergs was one of my best decisions.

 

[poolboy]

It's been a while and I'm starting to consider a 150HP upgrade again. I have decided to not go the supercharging route to keep the sounds as original as possible.

Someone was telling me dual Webers give more power--anyone have experience with this or know what kind of HP gain one might see? Keep in mind I have a GP2 cam and 9.5CR if that matters. Thanks for the ongoing discussion...

If you are going to try increasing the carburettors output thinking that will get you more HP, you might need to increase the displacement and slide in a more aggressive cam than the GP2.
Personally, I think I'd just go out and buy something else.

 

[Monkeywrench]

On the way to Breckenridge via Hoosier Pass in 2001, I noticed a buddy's TR3A blowing black smoke, even though he stopped twice to change jets in his DCOEs. I drove right to the top with my SUs, no black smoke (though it was running a little rich). Afterwards I touched up the mixture a bit with a simple turn of a nut with my fingers. No worries about spilling $60 jets all over the ground.

Webers are good carbs if set-up correctly. Problem is, most aren't and SUs are less 'tuner sensitive'. My .02

 

[MTribe]

Really appreciate all the comments as always!

RE which Webers. I recall the person saying Weber side drafts, so I assume the DCOEs. However it sounds like two of those wouldn't provide much more power than the dual Zenith Strombergs?

RE SUs. Huh, sounds like those are great to set and forget. But I'm assuming similar power level to Zenith Strombergs?

RE Triple carbs. I was originally hesitant to do this since two carbs is plenty to keep tuned well. I was thinking of going to modern fuel injection like MegaSquirt, but have come around to why I love this car--totally "analog." The engineering elegance is inspiring.

RE original PI fuel injection. I would really love to go this route, but couldn't find much on this. Anyone know where systems might be available?

RE power in general... I totally get the "if you want more power get something else" argument. However my goal is to get it to the original spec of 150hp. I have a Lotus Elise for the track, and wouldn't want to change the personality of the car with that much more power, anyway.

 

[TR3driver]

I'll make a radical suggestion : Get a copy of Kas Kastner's "Triumph Preparation Handbook" and read it. Kas founded and ran the US Triumph Competition department for many years; there is almost no combination (of 70's technology) that he hasn't tried on the dyno and on the track. He also wrote many of the factory "Competition Preparation" handbooks (although maybe not the one for TR6).
https://www.kaskastner.com/

You should already be close to what the factory called "150 bhp", assuming you also installed a tubular exhaust header and matched the stock carbs & ignition to the modifications. For a bit more, you could try a GP3 cam, do some light combustion chamber mods (from the book) and take the compression just a bit higher. In combination with the chamber mods, you should probably be able to run 10:1 on (premium) pump gas. Note that the later drop in the factory spec (to 135 bhp as I recall) was only partly due to de-tuning the engine for better driveability; they also changed their rating method to bear a bit more resemblance to the real world.

AFAIK, no one makes all of the parts for the old Lucas mechanical PI. You'll have to find a used original unit, probably from the UK, and then have it reconditioned (as suggested before). Even then, it is likely to be troublesome, have flat spots, and burn a lot of fuel. It would be mostly for bragging rights IMO; you'll get very little extra power from the PI. It's also hard to tune for other modifications (like the headers) unless you have the ability to accurately machine cams.

 

[justin_mercier]

The extra power from the PI system was more from less smog attatchments and the hot cam and not the lack of carbs. You need to remember that what they listed as HP back then is not what we usually consider the same number today. The measured the engine, without any of the 'inconvenient' things like... a fan, or tranmission attached, etc. The '150' hp engine is really more like 115 at the rear wheel if you actually dyno it. The US Spec 105BHP engine was only around 70hp at the rear wheel. If you want to go fuel injection, I'd recommend Rick Patton's TBI kit for the strombergs. it's not going to 'gain more power' by itself, but it will gain you reliability and more easy tuning of your air/fuel ratio through the power band.

 

[Darrell_Walker]

Well, fuel injection does have some inherent advantages over carbs:

1. No venturi, so less intake restriction (note, the Patton conversion may not have this advantage, given that it is a carb conversion)
2. Better fuel atomization

I don't know a lot about the TR6 PI system, but I believe it is port injection (one injector for each intake port), so an interesting idea would be to use the intake system, but replace the mechanical injection with a more modern computer controlled system (MegaSquirt?). Or there are various ITB (individual throttle body) components that could be used. You could also add a MegaJolt, and get complete control of both the fuel and spark. But I agree that is a very different kind of tinkering than carbs.

 

[Monkeywrench]

Well, fuel injection does have some inherent advantages over carbs:

1. No venturi, so less intake restriction (note, the Patton conversion may not have this advantage, given that it is a carb conversion)
2. Better fuel atomization

I don't know a lot about the TR6 PI system, but I believe it is port injection (one injector for each intake port), so an interesting idea would be to use the intake system, but replace the mechanical injection with a more modern computer controlled system (MegaSquirt?). Or there are various ITB (individual throttle body) components that could be used. You could also add a MegaJolt, and get complete control of both the fuel and spark. But I agree that is a very different kind of tinkering than carbs.

To a certain extent, yes, but I can't imagine a fuel injector from the 60s will atomize fuel better than a properly set-up carburetor. Modern injectors can for sure, but it's going to take an ecu to run it and everything is going to have to be custom made. I bet a modern flat side motorcycle carburetor would work better than a Lucas injection unit. Does anyone have pictures or video of the spray pattern from an old Lucas injector? I bet a Holley on a custom manifold sized correctly with a plenum would make very good power.

Also, induction mods will work only if they're the choke point. I have PipeMax. If anyone can fill in the following blanks for me, I'll post the information. Then it's a matter of just looking at flow charts to determine the proper venturi / carburetor size.

Connecting rod length (C-C)
Valve head diameters (intake and exhaust)
Valve stem diameter (intake and exhaust)
Valve lift
Duration @ .050
Degreed centerline
Lobe Center Angle
and port centerline length (not critical, but it will subtract this length for the exhaust pipe calculations)

 

[TR3driver]

Well, fuel injection does have some inherent advantages over carbs:

1. No venturi, so less intake restriction

Yes, but the restriction (when properly sized) only amounts to a few inches of H2O pressure drop, out of nearly 400 inches of head. Definitely worth 1 or 2 percent, but you're spending a whole lot of money for a power increase too small to feel.

The big advantage should be more accurate mixture, particularly when trying to get an aggressive cam profile to idle decently. With carbs and a lot of overlap, you get reversion through the carbs, which causes the air to pick up a triple load of fuel.

At the recent dyno day, the fuel mixture was on the display. Easy to see that with the cars with carbs, it wandered around a lot (with many of them being way rich at full throttle). For the last car of the day, one of the members put their late model Vette on the rollers and the mixture looked like it was being controlled by a computer.

I've been reading about direct injection lately. Sounds like a fun area to experiment with. They seem to be blurring the line between Otto cycle and Diesel cycle, with outstanding results. Apparently for cruise conditions, they can burn a ball of fuel/air in the middle of the cylinder, with a layer of plain air between the burning mixture and the cylinder walls. The result both reduces pumping losses greatly (because the throttle is still mostly open) and reduces the amount of heat lost to the cylinder walls (which is wasted energy). Wild!

Of course, what I would rather experiment with is the turbocharged variable compression ratio engine that SAAB was supposedly developing before they got bought out. That way you don't have to run around with (inefficient) low compression all the time, the computer can just knock it down when the boost goes up. 30 psi of boost on a 4-banger should be better than a naturally aspirated V8!

 

[Monkeywrench]

Well, I figured out some specs that I was missing, so I modeled Brosky's engine. I couldn't find .050 specs on the TH5 cam, so I made a guess at what the duration at .050 would be (228 @ .050). Back tracking from his dyno chart, I'm getting about 140bhp at 5200rpm. I'd believe this number before I believed the 150bhp at 5500rpm - I can't see factory ratings be real reliable. I'm leaving out a lot of information the program outputs, but this should be enough for conversation here. If you're interested in taking it farther, I'd suggest you buy the program - it's a super powerful tool for the money. Let me know what kind of exhaust header you're looking at, and I'll put up what it's suggesting.

152.338 Cubic Inches @ 5200 RPM with 95.00 % Volumetric Efficiency PerCent

Required Intake Flow between 90.8 CFM and 95.0 CFM at 28 Inches
Required Exhaust Flow between 72.9 CFM and 78.3 CFM at 28 Inches


600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 129.3 134.6 137.3 139.9
Peak Torque Lbs-Ft 144.8 150.7 153.7 156.7


HorsePower per CID 0.849 0.884 0.901 0.918
Torque per Cubic Inch 0.950 0.989 1.009 1.028


BMEP in psi 143.3 149.2 152.1 155.1
Carb CFM at 1.5 in Hg. 218 242 255 267


Target EGT= 1430 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 89.7 to 93.1 Octane required range
Air Standard Efficiency = 59.90925 % for 9.500:1 Compression Ratio


Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 120.4 147.4 174.4


----- Engine Design Specifications -----
( English Units ) ( per each Valve Sq.Inch area )
Engine Size CID = 152.338 Intake Valve Net Area = 1.624
CID per Cylinder = 25.390 Intake Valve Dia. Area = 1.651
Rod/Stroke Ratio = 1.537 Intake Valve Stem Area = 0.028
Bore/Stroke Ratio = 0.786 Exhaust Valve Net Area = 1.200
Int Valve/Bore Ratio = 0.493 Exhaust Valve Dia. Area = 1.227
Exh Valve/Bore Ratio = 0.425 Exhaust Valve Stem Area = 0.028
Exh/Int Valve Ratio = 0.862 Exh/Int Valve Area Ratio = 0.743
Intake Valve L/D Ratio= .292 Exhaust Valve L/D Ratio= .338
CFM/Sq.Inch = 55.0 to 57.5 CFM/Sq.Inch =59.4 to 63.8
Curtain Area -to- Valve Area Convergence Intake Valve Lift inch= .363
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift inch= .313




Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0370 1.00 CC = 0.0497
0.50 CC = 0.0185 0.50 CC = 0.0249
0.25 CC = 0.0092 0.25 CC = 0.0124
0.10 CC = 0.0037 0.10 CC = 0.0050


------- Piston Motion Data -------
Average Piston Speed (FPM)= 3241.33 in Feet Per Minute
Maximum Piston Speed (FPM)= 5356.32 occurs at 73.497 Degrees ATDC
Piston Depth at 73.497 degree ATDC= 1.6255 inches Cylinder Volume= 180.8 CC
Maximum TDC Rod Tension GForce= 1903.27 G's
Maximum BDC Rod Compression GForce= 969.12 G's




------- Current Camshaft Specs @ .050 -------


IntOpen= 9.00 IntClose= 39.00 ExhOpen= 39.00 ExhClose= 9.00
Intake Duration @ .050 = 228.00 Exhaust Duration @ .050 = 228.00
Intake CenterLine = 105.00 Exhaust CenterLine = 105.00
Compression Duration= 141.00 Power Duration = 141.00
OverLap Duration = 18.00 Lobe Center Angle (LCA)= 105.00
Camshaft installed Straight Up = 0.00 degrees


-Recommended Camshaft Valve Lift-
Minimum Normal Maximum
Intake = 0.365 0.393 0.432
Exhaust = 0.322 0.347 0.381
Max-effort Intake Lift = 0.453
Max-effort Exhaust Lift = 0.399
Minimum Intake Valve Lift to prevent Choke = .393 Lift @ 5200 RPM
Minimum Exhaust Valve Lift to prevent Choke = .347 Lift @ 5200 RPM




- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 37.994 (usually this Length is never used)
2nd Harmonic= 21.564 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 15.055 (ProStock or Comp SheetMetal Intake)
4th Harmonic= 11.849 (Single-plane Intakes , less Torque)
5th Harmonic= 9.614 (Torque is reduced, even though Tuned Length)
6th Harmonic= 8.088 (Torque is reduced, even though Tuned Length)
7th Harmonic= 6.981 (Torque is greatly reduced, even though Tuned Length)
8th Harmonic= 6.140 (Torque is greatly reduced, even though Tuned Length)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood


Plenum Runner Minimum Recommended Entry Area = 0.969 to 1.090 Sq.Inch
Plenum Runner Average Recommended Entry Area = 1.114 Sq.Inch
Plenum Runner Maximum Recommended Entry Area = 1.138 to 1.346 Sq.Inch


Minimum Plenum Volume CC = 302.9 [typically for Single-Plane Intakes]
Minimum Plenum Volume CID= 18.5 [typically for Single-Plane Intakes]
Maximum Plenum Volume CC = 2496.4 [typically for Tunnel Ram Intakes]
Maximum Plenum Volume CID= 152.3 [typically for Tunnel Ram Intakes]




------- Operating RPM Ranges of various Components -------


Camshaft Intake Lobe RPM = 4866 Exhaust Lobe RPM = 4531
Camshaft's Intake and Exhaust Lobes operating RPM range = 2783 to 4783
Note=> Lobe RPMs are only BallPark estimations


Minimum Intake Valve Lift to prevent Choke = .393 Lift @ 5200 RPM
Minimum Exhaust Valve Lift to prevent Choke = .347 Lift @ 5200 RPM


Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 5598 RPM
Current (Exhaust Valve Curtain Area -VS- Time) Choke RPM = 6346 RPM


Intake Valve Area + Curtain Area operating RPM Range = 4056 to 6056 RPM


Intake Valve Diameter RPM Range = 3598 to 5598


Intake Flow CFM @28in RPM Range = 3063 to 5063
___________________________________________________________________________


Best estimate RPM operating range from all Components = 3123 to 5123


Note=>The BEST Engine Combo will have all Component's RPM Ranges coincidingl

 

[Monkeywrench]

I tweaked the rpm peak and moved the VE % up one point to see what the engine requires to make 150bhp at 5600rpm (with 9.5:1 compression). This is what the op is shooting for. Don't concern yourself with the current camshaft specs. Look at the recommended value, choke points, and how much air the engine wants.

52.338 Cubic Inches @ 5600 RPM with 96.00 % Volumetric Efficiency PerCent

Required Intake Flow between 99.2 CFM and 103.9 CFM at 28 Inches
Required Exhaust Flow between 79.6 CFM and 85.5 CFM at 28 Inches


600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 143.4 149.2 152.2 155.1
Peak Torque Lbs-Ft 149.1 155.2 158.2 161.3


HorsePower per CID 0.941 0.980 0.999 1.018
Torque per Cubic Inch 0.978 1.019 1.039 1.059


BMEP in psi 147.5 153.6 156.6 159.7
Carb CFM at 1.5 in Hg. 237 264 277 290


Target EGT= 1425 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 89.7 to 93.1 Octane required range
Air Standard Efficiency = 59.90925 % for 9.500:1 Compression Ratio


Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 133.7 162.1 190.5


----- Engine Design Specifications -----
( English Units ) ( per each Valve Sq.Inch area )
Engine Size CID = 152.338 Intake Valve Net Area = 1.624
CID per Cylinder = 25.390 Intake Valve Dia. Area = 1.651
Rod/Stroke Ratio = 1.537 Intake Valve Stem Area = 0.028
Bore/Stroke Ratio = 0.786 Exhaust Valve Net Area = 1.200
Int Valve/Bore Ratio = 0.493 Exhaust Valve Dia. Area = 1.227
Exh Valve/Bore Ratio = 0.425 Exhaust Valve Stem Area = 0.028
Exh/Int Valve Ratio = 0.862 Exh/Int Valve Area Ratio = 0.743
Intake Valve L/D Ratio= .292 Exhaust Valve L/D Ratio= .338
CFM/Sq.Inch = 60.1 to 62.9 CFM/Sq.Inch =64.9 to 69.7
Curtain Area -to- Valve Area Convergence Intake Valve Lift inch= .363
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift inch= .313




Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0370 1.00 CC = 0.0497
0.50 CC = 0.0185 0.50 CC = 0.0249
0.25 CC = 0.0092 0.25 CC = 0.0124
0.10 CC = 0.0037 0.10 CC = 0.0050


------- Piston Motion Data -------
Average Piston Speed (FPM)= 3490.67 in Feet Per Minute
Maximum Piston Speed (FPM)= 5768.34 occurs at 73.497 Degrees ATDC
Piston Depth at 73.497 degree ATDC= 1.6255 inches Cylinder Volume= 180.8 CC
Maximum TDC Rod Tension GForce= 2207.35 G's
Maximum BDC Rod Compression GForce= 1123.95 G's




------- Current Camshaft Specs @ .050 -------


IntOpen= 9.00 IntClose= 39.00 ExhOpen= 39.00 ExhClose= 9.00
Intake Duration @ .050 = 228.00 Exhaust Duration @ .050 = 228.00
Intake CenterLine = 105.00 Exhaust CenterLine = 105.00
Compression Duration= 141.00 Power Duration = 141.00
OverLap Duration = 18.00 Lobe Center Angle (LCA)= 105.00
Camshaft installed Straight Up = 0.00 degrees


-Recommended Camshaft Valve Lift-
Minimum Normal Maximum
Intake = 0.393 0.423 0.465
Exhaust = 0.347 0.373 0.411
Max-effort Intake Lift = 0.488
Max-effort Exhaust Lift = 0.430
Minimum Intake Valve Lift to prevent Choke = .423 Lift @ 5600 RPM
Minimum Exhaust Valve Lift to prevent Choke = .373 Lift @ 5600 RPM




- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 35.326 (usually this Length is never used)
2nd Harmonic= 20.050 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 13.997 (ProStock or Comp SheetMetal Intake)
4th Harmonic= 11.017 (Single-plane Intakes , less Torque)
5th Harmonic= 8.939 (Torque is reduced, even though Tuned Length)
6th Harmonic= 7.520 (Torque is reduced, even though Tuned Length)
7th Harmonic= 6.490 (Torque is greatly reduced, even though Tuned Length)
8th Harmonic= 5.709 (Torque is greatly reduced, even though Tuned Length)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood


Plenum Runner Minimum Recommended Entry Area = 1.058 to 1.190 Sq.Inch
Plenum Runner Average Recommended Entry Area = 1.217 Sq.Inch
Plenum Runner Maximum Recommended Entry Area = 1.243 to 1.471 Sq.Inch


Minimum Plenum Volume CC = 326.2 [typically for Single-Plane Intakes]
Minimum Plenum Volume CID= 19.9 [typically for Single-Plane Intakes]
Maximum Plenum Volume CC = 2496.4 [typically for Tunnel Ram Intakes]
Maximum Plenum Volume CID= 152.3 [typically for Tunnel Ram Intakes]




------- Operating RPM Ranges of various Components -------


Camshaft Intake Lobe RPM = 4866 Exhaust Lobe RPM = 4531
Camshaft's Intake and Exhaust Lobes operating RPM range = 2783 to 4783
Note=> Lobe RPMs are only BallPark estimations


Minimum Intake Valve Lift to prevent Choke = .423 Lift @ 5600 RPM
Minimum Exhaust Valve Lift to prevent Choke = .373 Lift @ 5600 RPM


Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 5598 RPM
Current (Exhaust Valve Curtain Area -VS- Time) Choke RPM = 6346 RPM


Intake Valve Area + Curtain Area operating RPM Range = 4056 to 6056 RPM


Intake Valve Diameter RPM Range = 3598 to 5598


Intake Flow CFM @28in RPM Range = 3473 to 5473
___________________________________________________________________________


Best estimate RPM operating range from all Components = 3474 to 5474


Note=>The BEST Engine Combo will have all Component's RPM Ranges coinciding

 

[TRED]

One of these will give near 200 HP and you get a 5 speed upgrade too.
Skyline 2.5L
Wonder if it will still sound like a TR6.

 

[DNK]

It don't matter if it sounds like a 6.
It will go like ape Sh....

 

[TRED]

It don't matter if it sounds like a 6.
It will go like ape Sh....

Even has two pipes out of the manifold, nobody will even know its in there. LOL

 

[Gliderman8]

Wonder if it will still sound like a TR6.

Don't be concerned.... by the time they see your tail lights in the distance they will forget what they heard

 

[WedgeWorks]

If Group 44 can get 230hp out of their TR6 then 150 is more than reasonable. look at the PI TR6s.....150 out of the box. As previously mentioned here its all about headers, cams, induction, balancing, compression and all the little tweaks to get ever bit and also reliability.