Which Kelford Camshaft is Best for me? | 850-1000hp 2JZ Test
Question: I have a 3.0L 2JZ with a Precision Turbo 6870. What cams and boost are best for me? How much power should I expect?
Answer 1: For 850-1,050hp, we would reach for the T202-D i272°/e278° 10.20mm camshafts and expect:
23psi for 850hp / 630tq with a 1.0:1 Engine Pressure Ratio
28psi for 935hp / 710tq with a 1.1:1 EPR
35psi for 1,020hp / 795tq with a ~1.2:1 EPR
Answer 2: For everyone else, let’s call that 650-970hp, we would reach for the T202-C i264°/e272° 9.90mm camshafts and expect:
15psi for 650hp / 485tq with <0.9:1 Engine Pressure Ratio
21psi for 800hp / 600tq with <1.0:1 EPR
24psi for 850hp / 645tq with a 1.0:1 EPR
28psi for 910hp / 710tq with <1.1:1 EPR
31psi for 970hp / 760tq with <1.2:1 EPR
Purpose:
Real St.’s mission is to catalog various build stages and questions encountered by our customers’ most common engines and platforms.
The stock-stroke, un-ported cylinder head Toyota 2JZ-GTE and the Precision Turbo 6870 Next Gen are two very common choices in the racing community given that the 2JZ’s cylinder head can support in excess of 1,000hp without porting.
With Precision Turbo’s 6466 paving the way in 2012, the 6870 units followed at the end of 2014 and offered a “Goldilocks” type of application for so many engines used in racing, with flow capacity upwards of 1,000hp in appropriate packages.
After 10 years, Precision Turbo’s new 6870 Next Gen follows suit of the 6466 offering massive compressor flow for the 70mm turbine wheel family. The 70mm wheel performs well in a variety of applications from sub-two-liter drag cars, or twin turbo v8s and can efficiently support upwards of 800-1,050hp on a 3.0L 2JZ. The new Next Gen 68mm compressor wheel is rated at a massive 1,200hp.
An unported cylinder head and 3.0L engine size both are not suited to using 1,200hp of compressor wheel, but this is a common combination in the racing community, so we look to demonstrate what sort of airflow suits which camshafts and how to best utilize this turbocharger on your 2JZ project.
We aim to accurately conduct repeatable tests on our varied engine combinations while striving for operation under similar circumstances. Furthermore we aim to present the community with easy-to-understand and informative education in order to make informed decisions for their needs.
To do this, we need to first present the conditions at which the tests were conducted:
Intentional Starting Variables:
Test 1: Kelford T202-B Camshafts (260° Adv. Dur. / 9.60mm Lift)
Test 2: Kelford T202-C Camshafts (i264°/e272° Adv. Dur. / 9.90mm Lift)
Test 3: Kelford T202-D Camshafts (i272°/e278° Adv. Dur. / 10.20mm Lift)
Test 4: Kelford T202-F Camshafts (i282°/e286° Adv. Dur. / 11.25mm Lift)
Constants & Conditions:
Engine: 3.0L 2JZ-GTE w/ 9.0:1 C/R w/ Unported Cylinder Head
Turbocharger: Precision Turbo 6870HP Next Gen
Exhaust Housing: T4 Divided 1.15 A/R
Exhaust Manifold: Artec Cast T4 Divided
Intake Manifold: Plazmaman w/ 72mm Throttle Body
Intercooling: Plazmaman Air to Air
Fuel: One Ethanol 112S
Dyno: Superflow SF-Powermark
Engine Acceleration Rate: 600 rpm/sec
Conditions for Run 1: 4,000-8,000rpm & 100kpa (14.50psi) Target
Conditions for Run 2: 4,500-8,000rpm & 150kpa (21.75psi) Target
Conditions for Run 3: 5,000-8,000rpm & 200kpa (29.00psi) Target
Conditions for Run 4: 5,500-8,000rpm & 250kpa (36.25psi) Target
Avg. Starting Air Temp.: 82.2°F (27.9°C)
Avg. Starting Water Temp.: 176.8°F (80.4°C)
Avg. Starting Oil Temp.: 191.2°F (88.4°C)
Unintentional Starting Variables w/ >10.00% Deviation:
Avg. Density Altitude: 1,530.5’ [1,165-1,999’]
Test Notes:
We utilize a SuperFlow SF-Powermark Engine Dynamometer for our testing. This is a high-capacity water brake dyno that precisely controls load and speed of the engine using SuperFlow’s automated closed-loop systems to test high-output engines up to 15,000 RPM and over 2,500 HP.
For these tests, we looked to test the 6870 at various boost levels as we look at how the 70mm turbine wheel copes with the flow capacity of its 68mm compressor wheel. We also examine the effects of moving to larger camshafts by targeting the same boost levels for each test and showing you the differences in how the engine breathes.
The way an engine dyno operates and the data that we’re able to achieve is not always directly comparable to a chassis dyno. On a chassis dyno, the vehicle’s various components are still in play - torque converter, traction, etc. On an engine dyno, since we can load the engine at any RPM we want (even at idle), you cannot directly compare the early powerband of an engine dyno to a chassis dyno due to the elimination of those variables that affect spooling characteristics.
The entire turbo system remained the same between the four camshaft tests. All tests were performed through an Artec divided T4, twin-gate, exhaust manifold, through a Plazmaman air-to-air intercooler and a Plazmaman street intake manifold with 72mm throttle body on One Ethanol 112S fuel.
Results:
The 6870 straddles a power range with the 2JZ where we saw a breathing benefit at higher boost levels not seen at lower boost levels. We would pick the C camshafts for applications spending most of their time under 28psi, where the turbo very effectively and efficiently makes 600-900hp. The D camshaft does start showing gains, being worth 25+hp at 28psi.
Here you can see the full T202-B vs T202-C Results
6870HP NG T202-B Run 1: 609.7hp @ 7,500 & 14.7psi (20.88hp/psi) with 479.2tq
6870HP NG T202-C Run 1: 646.7hp @ 8,000 & 14.5psi (22.30hp/psi) with 484.8tq
6870HP NG T202-B Run 2: 745.8hp @ 7,800 & 20.8psi (21.13hp/psi) with 579.2tq
6870HP NG T202-C Run 2: 796.8hp @ 7,600 & 20.6psi (22.70hp/psi) with 601.4tq
6870HP NG T202-B Run 3: 872.8hp @ 7,600 & 28.1psi (20.49hp/psi) with 701.4tq
6870HP NG T202-C Run 3: 922.0hp @ 7,400 & 28.4psi (21.49hp/psi) with 718.0tq
6870HP NG T202-B Run 4: 957.9hp @ 7,400 & 34.9psi (19.39hp/psi) with 790.0tq
6870HP NG T202-C Run 4: 1,014.1hp @ 7,400 & 34.9psi (20.53hp/psi) with 815.0tq
Wow, massive gains at all boost levels on the C cams over the B. Let’s move to checking out if the gains continue with the D cams:
Here you can see the 6870’s performance between the C and D cams. The D Cams weren’t worth anything of note at lower boost levels, being worth a peak of 4.2hp at 20.6psi. However at 28psi / ~900hp, they demonstrated about a 25hp value.
Since the 6870 with the C cams makes 650+hp on 1 bar of boost and over 22hp/psi, this will be a very popular pump fuel combination for people. Gasoline applications may experience approximately 5% lower numbers, so take 30hp off of a 650hp expectation.
Q: If I choose the C cams, do I have to avoid running higher boost?
A: No - to a point. Even when we turned the boost up to 250kpa (36.25psi), the exhaust pressure only reached 1.25:1 by 8,000rpm. The efficiency of the combination is decreasing, and it would pick up from larger camshafts, but it is not in distress at this level.
However, this was only about 80% of the turbocharger’s maximum rpm (119,000rpm on a 148,660rpm limit), so it would not be able to support that without a substantially elevated Engine Pressure Ratio.
Interpreting these results:
All in all, our recommendation is to be honest about where you spend most of your time. If this vehicle will spend its life at 15-25psi, the C camshafts are the way to go. If you are looking to try to have the fastest-spooling 1,000hp turbocharger, then the D cams are better suited to 900+hp and should be used for those goals.
We tested even larger F camshafts and were surprised to experience elevated exhaust pressure. The extra overlap seems to not agree with exhaust pressure over 1:1, and reinforced the notion of matching the camshafts and turbocharger to the intended use case.
T202-D Run 4:
Power: 1,027.3hp @ 7,300rpm & 35.6psi
Peak HP Production: 20.50hp/psi @ 7,300rpm
EBP (& PR) @ Peak Power: 39.4psi (1.11:1 PR)
8,000rpm EBP: 41.9psi
8,000rpm Engine Pressure Ratio: 1.25:1
Turbocharger RPM: 119,000
T202-F Run 4:
Power: 954.9hp @ 6,400rpm & 35.9psi
Peak HP Production: 18.95hp/psi @ 6,400rpm
EBP (& PR) @ Peak Power: 36.3psi (1.01:1 PR)
8,000rpm EBP: 57.4psi
8,000rpm Engine Pressure Ratio: 1.66:1
Turbocharger RPM: 131,000
If you have any other questions about how to optimize your combination, give our team a call and we’ll be happy to help.
Special Thanks to:
Kelford Cams & Precision Turbo for their willingness to test and experiment to answer these questions with us, as well as Plazmaman and Artec who both contributed products used in this test.
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