250 xflow dyno charts

[pioneerxf 31]

Hi all,

On the path of deciding to work the crossie more or go the AU VCT road I started searching for dyno charts on the web. Seems there is bugger all for the ol trusty 250. I’d appreciate if people could post up any graphs they’ve had done. Good bad or ugly. Only interested in NA for myself but won’t discourage blown. Could be a good reference sticky (if it doesn’t exist already)

 

Few words on mods would be great guide eg removed spare wheel gained 5kW hahaha

[pioneerxf 31]

not even a torque power pull, sadface...

 

best I've been able to find so far crappy screen grabs from a video lol

 

 

trying to balance against a half decent VCT 4.0 see what impact mods have to the 4.1 to see if it's worth the work

 

 

yes I'm aware of dyno comparison differences, correction factors etc. I'm more interested in the where and when of the torque than absolute number

 

[deankxf 20,290]

probably better off asking a few tuners directly. 

 

[gerg 10,871]

You will always make more from an OHC over a Crossy for the same kind of work done. Conversely, it would take more money and effort to get a Crossy to perform as well as an OHC.

Stock carby Crossy made 92kW
XF EFI - 120kW
EA 3.9 - 139kW
EB XR6 - 161Kw
ED 4.0 - 148kW
EF 4.0 - 157kW
AU 4.0 -157kW
AU VCT - 172kW

So even going with the least powerful of the OHC motors is a huge step up from even the best of the 4.1 crossflow.

That said, I have big respect for the old crossflow 6. You would treat them like a small-bore, long-stroke, inline 6 version of a Cleveland. They take the same rockers, valve springs, share the same valve layout and combustion chamber design.

Good manifolds are expensive and getting hard to find. The EFI one is ok for stock power, but you'll hit a ceiling pretty quickly as the runners and plenum aren't terribly huge.

In my research on here over the years, it seems like at around 200rwhp, serious work needs to be done to squeeze any more than that out of it.

Folks on here have gotten 250, 300 even, but that's getting wild and not really a street engine any more.

You can't get much bigger valves in there, so you need to go bigger with the cam. You're pretty much limited to flat-tappet unless you spend up big on a custom roller setup.

Porting is a black art on these, as really the only gains come from opening it up more. On a clevo, especially 2Vs, you can gain big just by tidying up all the dags and ridges they come with, but with the Crossy you're already starting with a pretty nicely shaped port, it's just a bit small.

OHC motors can be hopped up too, but they also have their limitations, mainly in cam lift and spring pressure. Too much of either will break the standard rockers and aftermarket ones don't really exist except for custom ones. Jim Mock Motorsports had the gun camshafts for these a while ago, dunno if they're still going.

Hope this rant helps

Gerg

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[pioneerxf 31]

Much appreciated guys for the info. Yeah I’m still caught in that do I hot up the 4.1 and enjoy it for what it is. Or chase a bigger number and enjoy the newer designs. 
 

Haven’t got much feedback yet from engineers on the 4.0 legality in QLD. Costs for a 4.0 conversion and a decent 4.1 build are pretty close to comparable in most aspects. Feel the 4.0 may be more fun and more reliable but the 4.1 would be a bit more cranky and have some cred. 

[gerg 10,871]

Much appreciated guys for the info. Yeah I’m still caught in that do I hot up the 4.1 and enjoy it for what it is. Or chase a bigger number and enjoy the newer designs. 
 
Haven’t got much feedback yet from engineers on the 4.0 legality in QLD. Costs for a 4.0 conversion and a decent 4.1 build are pretty close to comparable in most aspects. Feel the 4.0 may be more fun and more reliable but the 4.1 would be a bit more cranky and have some cred. 

You could bolt a 4.0 from an XG in there using standard components, which the engineer will much prefer. You may be limited to a log intake vs the dual length (EF onwards) one due to spring tower clearance.

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