Bhp Figures

[daneldridge23 15]

hi guys

 

At presnt i have had my

• crank lightend balenced and knife edged
  
• conrods polished lightend and balenced
  
• pistons lightend and ballenced
  
• lightened and ballenced flywhell
  
• omex throttle boddies with 600 ecu
  
• piper fast road cams + pullys
  

 

now i am considering getting a big valve head but would like your guys opinion first on if another 800 quid is worth the bhp gain from this or not, also what power do you guys think i may produce when im up and running, i kno its only gusses but id still like a few figures

 

Dan

[Daviewonder 533 3 Cars]

What engine is it?

[daneldridge23 15]

mi16 1.9

[Anthony 1,003]

There should be the potential for something in the region of 200hp there, but as always, the devil is in the finer details and the setup.

 

The general consensus is that a big valve head is not needed on an Mi, and indeed on the smaller 83mm bore of a 1.9, potentially problemsome due to valve shrouding. There's a big pinned topic about it that you probably want to have a read of, but generally speaking, my opinion is to leave the head alone beyond a refurb and properly recutting the seats with the correct angles. The Mi head flows plenty as it is.

 

To give you some idea, if you have a read of Dr Sarty's build thread, you'll see that his standard Mi head made something in the region of 240-250hp with just a mild inlet cam (although admittedly on a 2.2 litre bottom end).

[brumster 135 1 Cars]

Ooo, estimates, fun! Ok, I'll punt forward the following, assuming those road cams are fairly mild :-

 

Before the head work : 178bhp

After the head work : 180bhp

 

Thankyou, I am available for kids parties also....

 

[daneldridge23 15]

well if i was going to get the valve job done any ideas on the best people to go to?

id love to get close to 200 on a n/a car

[welshpug 1,666]

leave the valves alone, higher comp pistons decent cams and longer inlet and better exhaust manifold

[Miles 331 1 Cars]

Cam spec, If regrinds then around 185, as the other work has no bearing at all or if better cams then the BHP depends on those, Who did the work?

[camgti 56]

As said above, don't bother with the BVH. Spend the money chasing compression and cams to make it all work well... The longer inlet will also work wonders

 

Cam

[brumster 135 1 Cars]

Although it was never dyno'd, I suspect I got somewhere between 190 and 210 depending on whether you wanted pub figures or real-world my arse dyno never complained, and it was relatively competitive in it's class for me to not worry too much about what the figure was. Hey, it drove and pulled nicely, that's the main thing. I won't bore you with the details; if you're interested :-

 

http://forum.205gtidrivers.com/index.php?showtopic=81038

[petert 601]

Definitely go chasing compression and squish height before big valves. Have a search for that thinner Cometic gasket. A can't recall the post but there's an excellent write up on the value of compression increase alone.

 

edit: found it

 

http://forum.205gtidrivers.com/index.php?showtopic=128397

Edited December 2, 2011 by petert

[daneldridge23 15]

That settles it i think 800 quid can be spent better else where, i heard somewhere about pitting a second spring seat washer in to compensate for my 3angle valve work is this true?

 

Dan

[welshpug 1,666]

only if the valve spring heights are incorrect.

[daneldridge23 15]

I have re cut seats aswell so they would be would they not?

[welshpug 1,666]

can't tell without checking them.

[petert 601]

If you cut the seats a second shim can only be good, not bad as it will also help the sagged old springs.