Xu9j4 Big Valves And Regrinds Cams?

[Sandy 191]

Knowing the power and flexibility some builders are getting on 34.5mm inlet valves..... To get 36.5mm valves to work better takes a disproportionate amount of development work and requires violent cam profiles. It really isn't worth it from what I've seen so far.

[DrSarty 90 1 Cars]

Knowing the power and flexibility some builders are getting on 34.5mm inlet valves..... To get 36.5mm valves to work better takes a disproportionate amount of development work and requires violent cam profiles. It really isn't worth it from what I've seen so far.

 

Which I hope goes to show what I said first off is pretty accurate.

 

I have nowhere near the technical engine knowledge that Sandy has, but I believe we've said the same thing, which is don't bother with the big valves; sell them on.

 

Invest your money in making what you have lined up already work as efficiently as possible, rather than following this route of excess, meaning big this and bigger that, which sounds like it works, but is often a route to disappointment.

 

It seems with knowledge and experience available on this forum, you will be able to achieve much more than you'd ever think you can with less.

[brumster 135 1 Cars]

Which I hope goes to show what I said first off is pretty accurate.

 

Absolutely, DrS, I concur. Speaking to Longman recently, they can get 250+ out of an mi16 head on standard valve sizes (not a standard head, I hasten to add, but we're just talking valve sizes here). We are lucky to have such cracking standard engines to work with, us Pug fans, aren't we

[niklas 1]

Knowing the power and flexibility some builders are getting on 34.5mm inlet valves..... To get 36.5mm valves to work better takes a disproportionate amount of development work and requires violent cam profiles. It really isn't worth it from what I've seen so far.

 

What one engine worker can do only with larger valves another engine worker can do only with standard-size valves... It really depends on the engine tuner and his philosophy! There are many ways to get nearly the same result...

[Sandy 191]

There are limitations to achieving the desired overall result with any method. Bigger valves are typically touted as getting the same power with "less cam", but that's a simplistic view that does not allude very well to the kind of cam profile that's required to fulfil that, or indeed to kind of delivery you get, which will often be thinner feeling and less responsive than is possible another way. Big valves are not the wonder solution some people insist they are.

[petert 588]

I concur with Sandy. Money is better spent in other ways for less, with better results. For example, for a guaranteed 180hp, I recommend decking the block and liners, my Stage I cam and chip. Decking the block/liners gets the compression ratio up to 10.8:1 and decreases the squish distance. This creates a very sweet and responsive engine, with more power and torque across the entire rev range.

 

From DrSarty's epic threat you will notice that not a lot of cam is needed to make serious hp (around 230ish). Admittedly he has 2187cc, but it still has a standard head.

[niklas 1]

There are limitations to achieving the desired overall result with any method. Bigger valves are typically touted as getting the same power with "less cam", but that's a simplistic view that does not allude very well to the kind of cam profile that's required to fulfil that, or indeed to kind of delivery you get, which will often be thinner feeling and less responsive than is possible another way. Big valves are not the wonder solution some people insist they are.

 

What's required from the cam profile? Do you need to increase the valve acceleration off the seat? Ie less duration, same lift, aggressive angles)

What's your experience of power output? With the wildest cams imaginable, what kind of power potential does standard-size vs big valves have? And at what kind of revs?

[niklas 1]

I concur with Sandy. Money is better spent in other ways for less, with better results. For example, for a guaranteed 180hp, I recommend decking the block and liners, my Stage I cam and chip. Decking the block/liners gets the compression ratio up to 10.8:1 and decreases the squish distance. This creates a very sweet and responsive engine, with more power and torque across the entire rev range.

 

From DrSarty's epic threat you will notice that not a lot of cam is needed to make serious hp (around 230ish). Admittedly he has 2187cc, but it still has a standard head.

 

How high can you go on the C/R on these engines?

Without going for race fuels!

Are there some point where the combustion chamber or the shape of pistons create problems? (ie hot spots)

I know it depends on cam profile, but if we stay with hydr lifters (and cams with reasonable duration)

[Sandy 191]

I don't want to give too much away publicly, but without getting very specific, the two main issues with bigger valves and relating cam profiles, are low lift gas speed and particularly on the XU, the risk of valve clip on overlap. The gas speed issue is less of a problem at high rpm, but can seriously hinder the mid range flexibility and throttle response. To work around these problems you'll need rapid acceleration and compromised cam timing. The net result is usually an engine that is very sensitive to cam profile and timing/inlet+exhaust tuning/headwork; which is typified by the Honda VTEC engines, mostly using "tight" moderate duration/high lift cam profiles with rapid valve opening/closing and relatively large valve sizes. These engines are often produce impressive numbers and work well at around 100-120bhp/litre, but tuning them beyond that exposes the problems with delivery, producing power through rpm rather than BMEP. The VTEC engines also have the luxury of not running the violent profile all the time, which allows the cam designer a little more freedom.

Using (relatively) modest valve sizes tempers the low lift gas speed well and allows alot more resolution when altering the cam profiles/timing and tuning the pipes. That helps with development a great deal, because the amount of dyno time required to refine the set up is greatly reduced and the cam profile design isn't so incredibly sensitive, so less profiles need to be tried.

Further more, using less violent opening/closing and smaller/lighter valves reduces valve train stress/wear/fatigue significantly; which for most people is a concern. You can do alot more to mitigate the unwanted side effects of long duration on modest valves, than bigger valves on tighter profiles.

 

CR wise, it depends alot on the overall engine spec, but I would say around 11-12:1 for most hydraulic follower engines. The XU 16v seems to resist detonation well generally, but you shouldn't run any more CR than you need to to clean up the mid range and part throttle performance.

 

Moderation in all things is key.

[Guest paulthai]

 

Every comment are welcome. Please......

[Guest paulthai]

I can sell you both big valves and reground cams. However, both together are a waste of time, in my opinion. Whilst there is a benefit in flow at lower lifts from a correctly done big valve conversion, the real gains come from over 0.350" lift. Whilst both of my regrinds for the Mi16 have a lot of area under the curve (see Sandy's recent post about XU9J2 cams) they both only open to 0.350". Ideally you need a new billet cam with over 0.400" lift. Have a look at the options on my website or Catcams.

 

I see you already have the big valves. Make sure you use a reputable firm to do the conversion. The guides need to be pushed back (and replaced) so that the throat can be recontoured to match the new seat diameter. Ask for before and after flow figures!

 

If it were mine, I'd go the whole hog and fit new oversize 33mm solid lifters as well. This way you're reconditioning the bucket bores (probably worn anyway) and you can fit a high lift profile that you can rev to 7500 all day long, reliably.

How much the cams Stage I Intake High Lift (new billet only)?

Please checking the shipping cost to Thailand.

 

I am not sure some item must use together with cams Stage I.

 

I try to send the personal message but your inbox full.

[Guest paulthai]

Now I was changed the big valves already. I expand the inlet port. Maybe the engine run first start on 12/03/2009.

 

If I have a good or bad news, I am post as soon as possible.

Edited March 10, 2009 by paulthai

[DrSarty 90 1 Cars]

If I have a good or bad news, I am post as soon as possible.

 

Believe us Paul, we all wish you luck and want you to get great results.

 

I think what has always been said here in answer to your first question was to help manage your expectations.

 

I'm sure you won't get 'bad news', you just probably won't get 180BHP at the wheels, and the big valves probably won't deliver quite what you were expecting/had been told you'd get, unless you really go to town and spend a lot of money on further head work and stronger internals.

 

What did you decide in the end on a basic spec? Are you still going to use a GTI6 inlet, and a rechipped/mapped standard ECU? What cam(s) did you decide on?

 

All the best.

 

Rich

[Guest paulthai]

Believe us Paul, we all wish you luck and want you to get great results.

 

I think what has always been said here in answer to your first question was to help manage your expectations.

 

I'm sure you won't get 'bad news', you just probably won't get 180BHP at the wheels, and the big valves probably won't deliver quite what you were expecting/had been told you'd get, unless you really go to town and spend a lot of money on further head work and stronger internals.

 

What did you decide in the end on a basic spec? Are you still going to use a GTI6 inlet, and a rechipped/mapped standard ECU? What cam(s) did you decide on?

 

All the best.

 

Rich

Thank you Rick. I pleased you.

 

Sure now I can not get the 180 BHP at the wheels.

I think maybe inceare only 5-10 BHP from standard.

 

I try to remap the ecu and The peterT cam and using the VR6 throttle body.

I am not sure about the GTi6 inlet. In Thailand GTi6 hard to find and get.

[DrSarty 90 1 Cars]

I am not sure about the GTi6 inlet. In Thailand GTi6 hard to find and get.

 

There are some for sale on here, and I bet PeterT can get one for you too. It's only a matter of price and sending it to you.

[Guest paulthai]

There are some for sale on here, and I bet PeterT can get one for you too. It's only a matter of price and sending it to you.

 

I waiting to run engine on 12/03/2009.

Maybe I order the PeterT cam and inelt GTi6 together.

[engine killer 6]

I waiting to run engine on 12/03/2009.

Maybe I order the PeterT cam and inelt GTi6 together.

 

before you spend your money on GTi6 inlet and VR6 tb, will you consider throttle bodies? i guess the improvement willbe very signicficant when comparing to it.

[Guest paulthai]

before you spend your money on GTi6 inlet and VR6 tb, will you consider throttle bodies? i guess the improvement willbe very signicficant when comparing to it.

Please Recommend me.

[engine killer 6]

Please Recommend me.

 

i think Jenvey's inlet and throttle bodies probably are the best you can get. but with this set up you need a ecu.

 

i am using Autronic it is good but not very perfect when regarding to controlling the air/cond idling. my friend is now dealer of of Autronic, MoTec, ViPec, Superchip and EcuTek, he said MoTec is for the very very rich and very complicate engine set up, Autronic is very good for non air-cond setup (race car), ViPec seems suit most budget user as it is cheaper and can handle air-cond idling very good.

 

i am not sure what you can get in Thailand but since there are few circuits there, you will be able to find someone to map properly.

 

for the size of throttle bodies, from my experience 45mm are far better than 40mm. would like to hear comment from others about any bigger size too

[Guest paulthai]

Top end images.

Just put the big valves only.

Expand port later........

 

 

[engine killer 6]

seems like you will have a lot of porting to do.

 

those nice big valves make me jealous.

[DrSarty 90 1 Cars]

>Engine Killer

those nice big valves make me jealous.

Why?

 

I'm interested because the technical comments in this thread seem to show that they're pretty much surplus to requirement.

 

Paul said that he has these already, so it was understandable that he used them. My point is they probably can't do any harm; but they won't necessarily do any good.

 

I was just interested in why you said that.

Edited March 12, 2009 by DrSarty

[engine killer 6]

>Engine Killer

 

Why?

 

I'm interested because the technical comments in this thread seem to show that they're pretty much surplus to requirement.

 

Paul said that he has these already, so it was understandable that he used them. My point is they probably can't do any harm; but they won't necessarily do any good.

 

I was just interested in why you said that.

 

 

have been thinking to try this out long time ago. my last engine rebuilt i gave dave baker quite a number of e-mails but the reply was he was fully occupied. unfortunately my mechanic said he is not confident enough to open the throat (valve seat) for me. so when something you wanted to get but couldn't, it becomes a "treasure"

 

lowering both radiator and a/c condensor to allow a longer trumpets trial and run it on dyno is actually the thing i want to get most.

[Guest paulthai]

VR6 TB installed on my friend car.

After porting and setup engine already.

 

I will rolling on Dyno. (16-18 March 2009)

After That I order the PeterT Cam for second rolling.

 

Maybe the first rolling can produce the 165-170 BHP@flywheel. I hope so.

And the second rolling with PeterT cam produc the 170-180 @flywheel. Wow...

Edited March 13, 2009 by paulthai

[engine killer 6]

my friend he owns a roller here in Hong Kong and his partner owns an engine dyno in mainland China, both are only used by my friend, he keeps saying the figure (output:XXXbhp) is not that important at all. Too many parameters and too many factors affecting the end result. same engine same setting but setting the parameter just a tiny little bit differently may differ the result signicficantly. the numbers should be treated as an indicator, and most importantly the curve shape. my engine is producing around 160 at wheels but it goes much faster than those mildly modded Civic Type-R (EP3) with 180bhp at wheels (from the same dyno).

 

engine dyno seems providing more accurate (or closer to accurate) figure. you have no wheel spin, no transmittion loss etc. temperature is high in Thailand and it affects the result alot too. surely the tuner and dyno can fix the figure up to your expection if you insist, but your feeling with your right foot and the g-force and the lap time are the things to bet your trust on.