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I have various 951 intakes here and not a one of them lines up correctly with my nice 2.7L head. Round not oval of course. This is on a 3.0L turbo build.
The aftermarket intake I just got has a larger throttle body but the runners going to the intake are still 2.5L sized. There's not really enough meat to port this correctly.
Am i missing out on some/most of the benefit of the 2.7L head if I'm running 2.5L sized intake runners? Or is the larger throttle body going to allow increased velocity down the runners to make up for it?
Turbulences will harm the flow if you don't port match the intake.
Have your short runner intake rewelded with more meat to port match it. This large turbo will be strangled with a stock intake.
Yeah, I guess what I'm asking here is how much difference it makes.
Stock intake, at least the couple I have, are 41mm runners ID, about 51mm OD. 2.7NA head is about 49mm wide. Valve is 47mm wide but doesn't open that far and is probably supposed to be the largest restriction in the system.
When I started this project a year ago, I read that the 2.7L head could be easily adapted with some port matching. But there's only 10mm to play with. I can certainly match the port, but the runner itself is still only 41mm.
I don't have a 2.7 NA intake to measure it's runner. That'd be handy.
But does this really justify the expense of having a custom intake fabricated? And if so, I should have went 16v.
Not sure I understand the problem. The 951 intake can easily be port-matched to the 2.7 NA head inlet ports. This is a non-issue.
But as I said the 951 intake will harm performance with such a large turbo. Are you sure you can't have aluminium welded to the runners of your short runner intake?
Another option is to size down the turbo and use the stock intake.
Yes you should have gone 16v if you want to mess with the exhaust also. LR is offering their 8v intake again and it has the option for being ported for the 2.7 head. http://www.lindseyracing.com/LR/Part...KELINDSEY.html
Well, it can be port matched technically, but at a very steep angle. I can't rake that angle back too far as I only have 10mm to play with after about 1/2 - 3/4 of an inch.
Even if I port match the end, and I could have the inside honed to some extent, the runners are still going to be 41mm. The ports lining up correctly doesn't solve this.
I've been going through some online intake calculations. The 951 intake on the 3.0L will have peak torque of around 4000 RPM. That's 41mm runner.
At a 48mm runner (matching the valve size), it's 5300RPM.
4000 seems better to me but of course this ignores flow (cfm) and focuses on velocity.
The slight bottleneck effect from enlarging inlet runners while they have a slightly decreasing radius won't prevent in any way the engine from running well.
Many folks increase inlet valve diameter on stock 951 heads without enlarging inlet ports without any adverse effect.
I would not take too seriously online calculators. It's mostly the cam that will dictate where your peak torque sits, all other engine components (turbo, intake, etc) being reasonably sized.
I run 48mm inlet valve and 48mm runners, and peak torque still sits around 4200 rpm which is where I was with the stock intake, but the improved ram effect from the shorter runners means the torque does not fall on its knees past 5500 rpm like with the stock intake and the engine accelerates faster between peak torque rpm and peak hp rpm, which is slightly above 6k. That's arguably a relatively short usable power band but when all components feel like they perform together in harmony instead of against eachother they IMO make for a much better drive than some torque queen which is only as far as the stock intake will get you, and that won't even be the case with such a large turbo. At least that has been my experience with the stock 9R cam.
I don't have a 2.7 NA intake to measure it's runner. That'd be handy.
I've got a 2.7 manifold I could measure if you need to know. I thought about cutting it and fabricating a short runner and Lindsey type plenum but I'm not sure it would be worth the hassle.
So the intake currently in my possession is the SFR intake. It has the 70mm 928 TB which is a nice addition. It also has shorter runners so I guess that is a benefit to higher rpms. But like I said, 41mm.
The turbo compressor outlet is probably even smaller. I'd love to get this thing flow tested. I wonder if I can set up that test.
I have a 951 intake port-matched to the 2.7L head and it works well. The motor had a mild performance cam and stock 2.7 valve diameters. The motor made 450rwhp on a dynojet with the ported-951 intake, and a stock intercooler and stock TB . With a 928 TB, SFR intake and SFR FMIC it made 500rwhp, but with about 3psi more boost. If you figure about 11.5 HP per psi (consistent with my dyno runs for this car) then that means the big intake, big intercooler and big TB combined to account for about 15hp. I don't know how much of that 15 can be attributed to the intake alone, nor how much more power it would have made with bigger runners. I've since reverted to the ported 951 intake, 951 TB and 951 intercooler, as I like the stock fit/engineering and the other stuff didn't do much for a street car. I suspect you are spitting hairs a bit re the intake runner diameters, and would suggest starting with a ported 951 intake and then test alternatives on a dyno to see what actually helps your motor and what doesn't. Everything else is just speculation and theory....
FYI, I'm running the Web 274 cam. And Michael Mount optimized the intake and exhaust ports for me so the head should breathe real well. Didn't want to let it down with an intake that restricted flow.
But to the point of maybe it doesn't matter so much, well, maybe it doesn't. I'm not sure it matters $1500 enough to me.
If I see 450HP out of this thing, I probably won't care either way. Not going after high HP numbers. I just don't think I'd be able to keep the rear planted at the track if I go too crazy.
I checked the 2.7 inlet manifold I have and it has oval runners, at the flange the inside dimensions are approx 47mm wide x 42mm high, excluding the opening for the injector. Hope this helps.
11-21-2016, 12:21 AM
951 Intake, 2.7L Head
