My friend is running a simple set-up on his B18c type-R motor. It has, Jun cams, skunk2 valves, springs and retainers along with a port and polish. The Bottom is just new rods and CTR pistons. Is the (70-68) throttle body good enough or is an upgrade needed (72-70)? Kinda dumb question, but not too sure about this. Thanks in advance.

 

I'd like to see before/after dyno used to answer this, because I've looked at software that leads you through the calculations (free -- internet) and talked to people (DPR)... and with NA especially don't see the need for anything bigger than what you have.

In fact, I'm using 65mm based upon the conversations I've had.

I'm building out a JDM R engine NA, like you. Went with Crower 63413 cams / springs, oversized valves, and stage VI headwork at DPR. Arias pistons at 84.5mm / 12.5:1 (ish) compression.

Not put together yet, so I cannot tell you much more.

Good luck.

Mark

 

That's one thing I heard, but it's so mixed with all the different styles of builds. I was thinking that even with what my friend has, there would be no need to go 72. I think 70 was large enough.

 

Personally, I lean towards 'too big' at 70mm. Larry Widmer (The Old One) has an article describing his NA build of a 2.0L engine (84.5mm bore)... and while the intake is a modified Skunk unit, the TB is...

64mm

http://www.theoldone.com/articles/badtothebone/

There is a relationship between intake volume and TB size that I've read about... and what the tradeoffs are I don't recall. I think the larger volume may reduce air velocity somewhat -- which may reduce responsiveness at lower RPM.

Nothing is simple, is it?


FYI -- Mark

 

And he feels that he would not make anymore gains with a larger throttle body with a port matched manifold? If this is all true then there were a lot of misconceptions and wastes of money.

 

for a 1.8L, the stock itr throttle body will be the best.
dont port match the manifold either.

 

Ok I understand that, but my friends mods is whats confusing me. Anyone else to add light to this???

 

Your friend hasn't modified his as much as TOO had (in the article). So I'm sticking with the "it's already a bit large" position for now.

Larry is responsive on e-mail, I've read, so you might drop him a line. The contact address should be available if you follow that link.

Yes -- I think there are a *lot* of misconceptions out there, and a lot of money needlessly spent -- or worse -- that just degrades performance. The more I read and learn, the more amazed I am at how everything interacts and the incredible balancing act it takes to get everything working just right. You cannot learn too much before launching your project.

Take care,

Mark

 

Thanks Mark I will look into that further. Thanks for the comments. Take care.