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Discussion Starter · #61 ·
I myself see two separate questions to address.

1. Would there be an advantage to higher output above the current peak at/near 7K rpm or so? Answer yes, definitely. It should be obvioius that if you are revving in that range then more output makes the car faster, even with a 8K rev limit.

2. What the heck is the deal with the 8K limit on the e153. Lots of contradictory info on this one. Some builds report shifting without problem at 9k. Others start having issues as low as 6.5K. It has been suggested that this could a clutching issue rather than a internal trans issue. I myself have no problem shifting at 8K. Just lucky, I guess? If I did not have some reservations about taking my hydraulic lash adjusters aka lifters above 8K, then I would try upping the rev limit to see what happens. With solid lifters I would not have this fear of spitting. Solid lifters along with oversize valves are on the goodies wish list.
Not shifting at high RPM is mostly due to clutch moment area of inertia being too high for the synchros. Simple solution - go to a smaller clutch disk since this is proportional to R^2 of the disk. A single 7.25" clutch disk can probably just hold a 2GR's torque reliably. A twin 7.25" disk would easily hold it and still drive pretty nicely with a typical ~10-12 lbm flywheel.

I'm not sure if I am getting the meaning of this: "it can quickly spiral into extra capacity if you can get the stock valve seat to work."

I see a lot of online debate about larger valves, do they help, do they hurt (by reducing port velocity), are they just plain useless.

Re the cams there is a new billet cam offering from Piper. "Fast" cam with 270 duration, "Ultimate" cam with 285 duration. I don't know how these are measured. Compare to 256/266/272 for MWR Stage 1/2/3. Again, I don't know how these are measured, i.e. at what clearance. It could be that Piper and MWR are measured at the same clearance - or not.

Another possibility for a budget build is to adapt a high-duration cam from a 2gr-fks. The simulated Atkinson cycle requires much higher duration cams, but I don't have their spec. . Someone is taking this approach with the 2AR. PS. I have just been informed this can be scratched off the list, it is a no-go, because of different camshaft construction.
Sorry, brainfart there. Was listening to a meeting while typing. Basically, changing valves can quickly spiral to a lot of additional work to fit them. Some valve seats can't even take +1 mm sized valves well (the valve ends up sitting too far out for the seat to really support it well with high spring rates and high RPM usage).


I looked into the 2GR-FKS cam specs, and they actually weren't much longer than 2GR-FE cam duration. 8 degrees or so according to the engine data FSM? I was surprised they were barely longer duration.
 

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Discussion Starter · #63 ·
Keep in mind the valve actually sits on a hardened seat that's pressed into the head. It looks like there's not much room to expand that seating surface out, especially on the intake valves (look like they're completely covering the seats). You can just see what I believe are the exhaust seats. It's much easier to tell which is which when the valves are out.
 

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I myself see two separate questions to address.

1. Would there be an advantage to higher output above the current peak at/near 7K rpm or so? Answer yes, definitely. It should be obvioius that if you are revving in that range then more output makes the car faster, even with a 8K rev limit.

2. What the heck is the deal with the 8K limit on the e153. Lots of contradictory info on this one. Some builds report shifting without problem at 9k. Others start having issues as low as 6.5K. It has been suggested that this could a clutching issue rather than a internal trans issue. I myself have no problem shifting at 8K. Just lucky, I guess? If I did not have some reservations about taking my hydraulic lash adjusters aka lifters above 8K, then I would try upping the rev limit to see what happens. With solid lifters I would not have this fear of spitting. Solid lifters along with oversize valves are on the goodies wish list.
Yeah, unfortunately there's only two ways to really make NA power. Displacement, or RPM (and getting it to breath at those RPMs of course). See sport bikes and F1 cars for example. Ignoring of course minor things like reducing friction and other parasitic losses. So I do realize that you will probably have to rev higher to make substantially more power.

I don't disagree, it seems like there are other things going on. Clutch dragging just a little could certainly do it. It seems some people have more issues than others, could also be that some people expect a shift in a tenth of a second (for example) and if it takes three tenths they declare the transmission won't shift above xxx RPM. Just saying it could be an issue of expectation more than a physical limitation. I always felt like mine shifted OK at 8k (on my 3S), although again, I don't know if I was trying to shift quickly by other peoples standards.
 

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After a bunch of distractions, I finally got around to taking a very close look at the valve seats. Since I was taking the engine apart, I decided to use the opportunity to make one of those popular "Teardown videos," kind of like an unboxing video for mechanics. Ha ha. You can use the chapters in the video description to skip ahead to the relevant part for the valve seats - around 26:30. I don't have a lot of experience with this but I don't really see a way to enlarge the valve seats and valves without boring out the head a few mm. A 97mm bore versus a 93mm bore adds 2mm all around the radius and gives enough room to add 1 or 1.5mm even to the valve head. 97mm is also nice because somebody already makes a head gasket for this bore and pistons at different compression ratios for same. Why I am hung up on this is because I don't think the engine breathes worth poo above 7,000 rpm no matter what else you do to it - both torque and HP start to drop like a rock at this point - and I am looking for ways to make it better - I am talking purely NA, not interested in just upping the boost to force more air in.

 

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Discussion Starter · #67 ·
I don't really think the 2GR is that limited by the valve sizes. To compare to a fairly optimized 6 cylinder that's a bit older than the 2GR, the BMW S54B32 (E46 M3 engine) has 35 mm intake, 30.5 mm exhaust. The 2GR valves are 38 and 32 mm.

A modded S54B32 will belt out 340-350 rwhp on those stock sized valves with bolt-ons and big cams. Now what an S54 probably has, even with smaller valves, is better head flow than a 2GR.

I think some careful porting around the short radius and bowl of each port can probably add a solid 10-20 rwhp, and would enable better gains from more aggressive cams. Then it's just a matter of putting enough compression on it, and revving it out.

If you had enough head flow and cam, there's no reason a 2GR-FE shouldn't be peaking power out in the ~7800-8000 RPM range and making 350-375 rwhp. You'd need to be spinning it to 8400-8500 RPM to take advantage of that powerband, but given how many people spin them to 8k RPM, it's probably doable on a largely stock engine with valve springs. But it could definitely be one of those things where every 100 RPM you go past 8k, you're putting a ton of wear on the engine - usually in the form of a vibrational mode getting excited and starting to chew up bearings and/or timing chains. But my money is on it probably being fine given the short V6 crank.


Just my 2 cents, good cams + headwork is the ticket.
 

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Just my 2 cents, good cams + headwork is the ticket.
I've cleaned up the heads to take a better look. There seems to be some potential. Any of the youtube head porting gurus would have a field day with these heads. When I have some time (after I am done shopping for cartridge rolls and carbide burrs) I'll document this better.
 
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