Marvelous - i'm only messing really - the weird thing is that the two cars have always been so close in the power torque and track abilities. Also the drivers too are very similar so we have had many years of chasing each other around the track. Just wondering whats changed so much after we both put in the same cams ...?
Different engines - clearly respond differently to the cams - little things can make all the difference as can the exact timing of those cams and ignition etc Also different days - we will see how everyone compares very soon. Cheers Rob
You should be able to get my plots from Vince soon as I'm going to the RR day on the 14th of March. Hoping for anywhere between 190-200+ and similar torque figures to Matt D's car which is very healthy 154lbs Will be interesting comparing like for like cars on the day. I went in Matt's car at Mallory and his unit feels very strong everwhere the torque really felt it's presence known low and high in the Rev band.Nice spread of top end power and torque across the spectrum. I'm sure when it done a few more miles it will break 200bhp with ease....it's a new block. BTW heads are usually polished and not flowed. The same guy does AmD Stealth TSR and BR Motorsport if you did not know. Ianb
"BTW heads are usually polished and not flowed. The same guy does AmD Stealth TSR and BR Motorsport if you did not know." hope not mate, polishing is a bit daft next time at vinces someone take a disc and get all the 2.0 valver runs, and i'll plot em all up for you
The cylinder head is THE MOST IMPORTANT area to be considered by the serious tuner. It's design has more bearing on the end result, performance-wise, than any other component of the engine. There is no way that high horsepower can be obtained if the head wont flow efficiently, and in turn burn that air/fuel mixture efficiently. It is often thought that there is a direct relationship between high air-floe numbers and high power output. In priciple this theory sounds correct, but in practice it doesn not always work out that way. At one time an American manufacturers factory racing depertment picked 'the best' high performance heads from the production line for modifying. After being ported, each head was flow checked. The heads that recorded the best flow rate where kept for the factory racing team. The other, lesser heads, where sold on to selected independant and privateer teams. Interestingly, on the Dyno, the heads that produced the best flow rates actually recorded lower power figures than the engines with the lesser flow rate heads! Going on from the relative simplicity of flow rates you have cylinder head 'swirl.' Swirl is defined as the directional effect imparted to the inflowing gas by the shape of the inlet port, or its angle of entry into the combustion chamber. Swirl assists eventual combustion by causing the mixture to be evenly and homogenously distributed in the cylinder. At th end of every exhaust cycle there is always a ceryain amount of exhaust gas that is left unscavenged in the cylinder. If this exhaust gas is allowed to collect into a pocket, it will retard the ignition flame travel, even preventing quite an amount of the fuel/air mixture from burning. Good swirl will prevent this pocket of exhaust gas from forming by evenly mixing the fresh mixture coming into the cyinder with the unscavanged exhaust gas.
WHOA where did that come from tub ??? You been eating those theasaur's again ? I know i cant even spell it - who cares !
Indeed cylinder head is very important, look at a rover V8, big capacity but very poor head design=not big power per litre or look at a hayabusa, corking head design, lots of air pumped in and out, allowing high revs and big big power. however I have no idea why Barny [note spelling ] and Paul have such widely different graphs unless the temp was very high on barnys run and the software is not correcting for it
I have to disagree. Polishing on its own is a totally pointless exercise, only for bling, its the flow characteristics that matter and how evenly/completely the fuel distributes in the air Rob
Following on from the head thing, I have a suggestion for you to look at on the head of your Jetta Paul - see if the cast starts with an 027 or an 051. Barny's I'm certain will be an 051 - all the 16v heads (KR, 9A, ABF) all had the same cast (except one), they just ended up with slight variances depending on its use (I wont go into detail of what I have found). The point I'm making here is that all the 16v heads bar the early 16v KR head had a 051 cast as a starting point. The 027 (early 16V head) is reputed to be of better design. I dont know for sure, but have heard from more than one source, so perhaps that is where the difference is? I know that my '88 valver came with an 027 head, and I know that GVK's '87 has the same A better flowing head would be more apparent with wilder cams would it not??? It would make sense to me with all the work in a RE2000 engine, they would only pick the best components
can't be just the head casting, although ABFs have smaller ex valves, something in the sparks/fuelling i think
do 9a and kr heads have the same valve sizes? is the main difference that kr inlet ports are larger than 9a, and 9a exhaust ports are larger than kr?
That's what I've always believed Dex, the 027 head I have the inlet ports are MUCH bigger than the 9A head There's a thread on Vortex where they've cut a 16v head in half so you can see the port differences. good thread..
Interesting pic showing supposed flow rates of the 2.0 head, the 1.8 head and a flowed head. Here The 1.8 Intake out flows the 2.0 and the 2.0 exhuast out flows the 1.8. Joe
