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pf.

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Everything posted by pf.

  1. Well sir what field of work are you actually in? Yes I quote stuff but I do know what I am talking about after years in the trade you get a certain nitch at working with cars. Also I quote stuff as I don't want to blur the meaning of the original writer and do not want to take credit for someone else.
  2. I never said that a 30 head would outflow a 26 head I did say that it might outflow a 25 head. Now what I am saying is yes I can use a 26 head but this would put the cost up very high for the small gain it gives. Remember this is a leftovers engine I will build it right but I wont spend big on it. My name is not Al I did not want anyone to know my name so I lied but I will be truthful my name is Pat Famington and I do not own a 1500hp gtr I just thought that would be funny to write The reason I thought saying I had a 1500hp gtr would be funny is of course we all know here that it is nigh on impossible.
  3. Also I never said he was my engine builder I would not send any of my parts to him, not due to his workmanship just because I think he is a cock. But I have my engine builder mates that are well and truly capable of building a donk I just need to send the head away for porting.
  4. Also a point I want to make is that making a proper tuned exhaust is so much cheaper and easier with a 30 over a 25 head yes this is not of concern with turbos but n/a it is. To make the correct exhaust for a 4v head you need some very good metal skills as a oval port just doesn't cut it for a high power tuned n/a exhaust, round ports are so much easier to cater for.
  5. You are new to engine dynamics by the sounds of this there are many factors that give a two valve head a performance advantage at a cost ratio to four valve head. Yes four valve heads can flow higher numbers but cost a whole lot more to build think about it I am going to use bigger valves so I only need half as many and so on down the valve chain. I'll edit in some other facts soon. Quoted " You can't beat the quench & flame travel characteristics of a good 2V head, nor can you beat the pressure recovery characteristics & efficient discharge coefficient than can be achieved. 4V only have the curtain area advantage, other than that they are inferior in every way. That curtain area advantage is a big one tho & makes up for the other shortcomings at higher rpm. Bet most people don't realise the curtain area advantage is not as big as it looks on paper tho - valve to valve shrouding reduces the effective curtain quite a lot & the necessary placement of the valves requires more valve/bore shrouding as well, also direct acting cam on bucket setups are significantly lift limited compared to rocker arm setups. A canted 2V head can place the valves away from the cylinder wall so that the curtain area available can be almost fully utilised with fairly even discharge around the whole circumfrence of the valve - that makes for a very efficient intake tract with little or no 'wasted' volume. Compare that to a 4V head with it's shrouded valves, which must have port/bowl area above them even in areas that are innactive - resulting in less efficient use of the port volume, lower pulse tuning 'signal' & lower velocity ram effect. In short - a well developed 2V head can outperform a 4V head up to the point where curtain area becomes the restriction in the 2V head, from there the 4V will outperform. Oh yeah, you also have excessive pullover & reversion on 4V heads - by their very nature low lift flow is good, too good in many cases, something that flows well in one direction usually flows quite well in the other direction, so at lower rpm 4V engines experience higher rates of reversion (that's why they are doughy down low, got nothing to do with big ports). They also waste more potential trapped VE out the exhaust as that high low lift flow comes into effect at higher rpm during the overlap period." Also with the ve-volumetric efficiency you do realise that the scavenge effect can draw air through the intake faster it is called induced exhaust sometimes. This is the whole Idea of using tuned extractors so the crate a scavenge which will induce air flow. Do you even know that compression increases with rpm it is called dynamic compression this is what I mean by you don't understand the dynamics of a engine, you just quote paper figures.
  6. Oh yea I don't think he told me I could make 350hp but after seeing his recent builds I think he could but I am not using this guy. I have local mates that are builders so ill look around for a good head porter and get my mates to build it.
  7. Yea I am talking flywheel hp. The engine builder I am referring to has built 2v 6cyl race engines up to 350hp fly he said a rb30 build could see me at 350 fly I trust this guy's words. Edit here is his words quoted. BMW E20 engine, 2.8L, 2 valve per cylinder, SOHC, E85 fuel (I did the head & intake, specced the cam & provided specs for headers etc) 260rwkw (351rwhp) @ 8000rpm. That 120% VE @ 8000rpm. Tis only fed with 45DCOE's with 40mm chokes as well. I predicted it'd peak at 7800rpm, so I got it wrong by 200rpm, I was short 40hp on my estimate as well. Another engine that made exactly the same peak power (not a BMW engine) went on a engine dyno shortly after & made a tad over 400hp - so it's a pretty good bet this little beamer is doing about the same. PS - 2.3hp/ci f**k yeah!
  8. Also a advantage of using the smaller stroke of the 25 block means if I get a cam for 8k then it will spin up easier.
  9. There may be air in the system still, yes it should have a prop valve. My guess is that there is air somewhere up high in the system near the master or prop valve. Also what is the camber difference it would have to be huge to make a difference to rule it out let the front right tyre down then test again.
  10. Well I already have a 25/30 so I was going to recycle the leftovers. A engine builder has said he can build a 30 head to flow better for alot less in fact he believes the 30 head will flow better allround. I do not want any talk of 25/30's as I already have one being built it will be turbo. Edit at the end of the day a 25 or 6 head could flow better particularly the 26 head I doubt the 25 head would for n/a but it will cost a lot more money buy more I mean like 3 times the cost. The engine builder I spoke to said he could get me upto 350hp or more with a 30 head that is on a 30 block though.
  11. Hi all what would be the go with this what would I need to mod the head or the block? Also how and what would I do to do this. Also I do not need anyone telling me to use a 25 head there is reasons why I am doing this I could work it out myself but want to fast track the process. Thx for helpful responses in advanced.
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