SR20DE heads......

Can anyone tell me the difference between the P11 head and the "high-port" heads?

I've currently got a high port head in my race car, but have been told by a fairly knowledgeable person that more power is available from the P11 head. The current head is ported, but it's also at it's limit without spending serious $$'s. It's got cams, throttle bodies and other bits and pieces, so a head with more flow would be a real bonus. As you can imagine, I'm keen to find out the difference between the 2 heads if anyone knows. I've tried searching the web far and wide, but with no success......then I found you guy's and I'm desparately hoping that someone can help. Please? Help?

Originally posted by Group3J
Can anyone tell me the difference between the P11 head and the "high-port" heads?

I've currently got a high port head in my race car, but have been told by a fairly knowledgeable person that more power is available from the P11 head.

Eh???

That is not the thinking here. My understanding is that reason Nissan changed the port configuration is emissions. The high port manifold had the injectors wetting the manifold and this caused emissions issues. But a Nissan engineer here feels the high port head is worth at least 10 hp more than the low port.

Basically, the ports in the high port head have a pretty direct route to the combustion chamber. In the low port the air flow must turn a sharp corner to get to the combustion chamber.

Otherwise, it's pretty much the same.

Interesting..........

My view is more or less as you said, in that the high port head should flow better due to the more direct route to the combustion chamber and also because of the valve angle in relation to the port. Having said that, I give this person credit for being more knowledgeable than myself - although everyone can be wrong.

Don't suppose anyone has had the chance to do a flow comparision between a GTiR head and a high port head????

Originally posted by Group3J
Interesting..........

My view is more or less as you said, in that the high port head should flow better due to the more direct route to the combustion chamber and also because of the valve angle in relation to the port. Having said that, I give this person credit for being more knowledgeable than myself - although everyone can be wrong.

Well, I understand. My information comes from a Nissan engineer who use to also build engines for Toyota's GTP program.

The low port head seems to gain more power for equivelent mods, but only to a point.

Originally posted by Group3J
Don't suppose anyone has had the chance to do a flow comparision between a GTiR head and a high port head????

Actually, a GTi-R head is a high port head.

I see, so what your saying is that the high port head has more peak flow overall, but in terms of build up comparison, the P11 head will flow the same amount until you start getting to, say, the last 90%?

I see. I know that the GTiR head is different from a number of head's I've seen (all of which have been high port - never seen a low port head), eg it uses round inlet ports instead of oval, different manifold stud pattern (for the TB's I realise), it's got the solid posts instead of the HLA's, etc. I'm wondering about the actual port shape, specifically in terms of port diameter, flow characteristics (ie swirl &tumble), what sort of flow figures they produce from factory and shaping of the bowl area.
I was a little disappointed with my SR head in it's ability to flow in comparison to the Toyota 3S-GE head. On an average of the figures from 2mm-12mm of lift, the Toyota head outflowed it by 36cfm. I'm wondering if they gained more flow out of the GTiR head, considering it was a bit of a homologation special.........well, kind of.

Originally posted by Group3J
I see, so what your saying is that the high port head has more peak flow overall, but in terms of build up comparison, the P11 head will flow the same amount until you start getting to, say, the last 90%?

I don't know if I would go quite that far in making a statement. For one thing, the low port seems to start out at a bit of a disadvantage. It essentially catches up to the high port. But, it does seem to run out of flow based upon some development work that has hit a ceiling of sorts.

Originally posted by Group3J
I see. I know that the GTiR head is different from a number of head's I've seen (all of which have been high port - never seen a low port head), eg it uses round inlet ports instead of oval

Really? I don't remember this from my research into using a GTi-R manifold on my DE. It's been 3 years since then however so my memory may just be fuzzy. I know the GTi-R port is definitely shaped differently, in part due to the injector placement and the need to allow for the injector spray in the ports. Where the DE port has a hump at the top of the port (IIRC), the GTi-R has a hump in the bottom of the port (or is that vice versa?).

Originally posted by Group3J
I'm wondering about the actual port shape, specifically in terms of port diameter, flow characteristics (ie swirl, tumble, etc), what sort of flow figures they produce from factory and shaping of the bowl area.
I was a little disappointed with my SR head in it's ability to flow in comparison to the Toyota 3S-GE head. I'm wondering if they gained more flow out of the GTiR head, considering it was a bit of a homologation special.........well, kind of.

Well, I don't think anyone in The States has done any serious flow work on the GTi-R head. They just don't exist in any real quantities here. OK, they don't exist in any real quantities anywhere, but I think y'all have more than we do.

Unless the guy who looked up the fishe for me at Nissan got it wrong (which is certainly possible), the SR head I was looking at did indeed have round ports.

I didn't realise the injectors were in a different place on the GTiR head (although given the different induction arrangement it'd make sense)! Are they closer to the head for further away? High port head has the injectors on top, placed right near the head and the recess (hump) is at the top. So the GTiR injectors are at to bottom?

Yeah, understandably, not many guy's have played with them. There's a guy who races a GTiR in my class and even he know's very little about the head. I'm contemplating basing my Grunter SR on the GTiR motor, but I first need to establish that the extra cash is worth it. I can obtain an engine with ease from an importer, but they're worth in the order of $3000 Aust for the engine only (have a look here if you're interested http://www.sssautomotive.com.au/Nissan.htm). Given that pretty much everything will be replaced (pistons, rods, valves, etc, etc), the only reason I'm interested in using it is if the head can flow more.

Originally posted by Group3J
Unless the guy who looked up the fishe for me at Nissan got it wrong (which is certainly possible), the SR head I was looking at did indeed have round ports.

I didn't realise the injectors were in a different place on the GTiR head (although given the different induction arrangement it'd make sense)! Are they closer to the head for further away? High port head has the injectors on top, placed right near the head and the recess (hump) is at the top. So the GTiR injectors are at to bottom?

My memory is just a little too fuzzy at this point. I used to have a series of detailed photos of a GTi-R manifold.

NEWS FLASH!!!

I just found the photos! Attched is a photo of the GTi-R manifold ports.

Originally posted by Group3J
Yeah, understandably, not many guy's have played with them. There's a guy who races a GTiR in my class and even he know's very little about the head. I'm contemplating basing my Grunter SR on the GTiR motor, but I first need to establish that the extra cash is worth it. I can obtain an engine with ease from an importer, but they're worth in the order of $3000 Aust for the engine only (have a look here if you're interested http://www.sssautomotive.com.au/Nissan.htm). Given that pretty much everything will be replaced (pistons, rods, valves, etc, etc), the only reason I'm interested in using it is if the head can flow more.

Where are you in OZ? Do you know who Glen "Lumpy" Campbell is? If not, I need to hook you up. Lumpy is very familiar with the SR20 engine and in fact is the bloke who sent me the photos. He had this manifold available for sale if I wanted it.

His website is: http://www.driftdivision.com

No, I don't! Please, I'd love to chat to him.

I'm in the ACT.

Are those the GTiR TB's??????? Woah....damn you Mr Nissan!!! Bolt pattern looks similar to a high port engine..... And injectors in the bottom....that's just freaky!!!!!

G-Force...I think this question "What's the difference between high port and low port should be posted in FAQ. This is an interesting topic.

Originally posted by Group3J
No, I don't! Please, I'd love to chat to him.

I'm in the ACT.

Are those the GTiR TB's??????? Woah....damn you Mr Nissan!!! Bolt pattern looks similar to a high port engine..... And injectors in the bottom....that's just freaky!!!!!

You should be able to contact Lumpy from the web site I posted. If you have trouble reaching him, let me know and I'll send you a private message with his e-mail address.

Yes, those are GTi-R TBs. The bolt pattern is similar to the DE pattern, but indeed is different. It would also require reshaping the ports on a DE head to be able to use them.

Yes, very interesting. I'm assuming you need to make a recess for the injector? Any other mods? Port shape appears identical to the DE head. Do you know if it's the same ID?

Originally posted by Group3J
Yes, very interesting. I'm assuming you need to make a recess for the injector? Any other mods? Port shape appears identical to the DE head. Do you know if it's the same ID?

I don't know. I think the GReddy manifold for your car would be just as effective. The quad TBs will add some throttle response, but not likely any additional hp.