Bhp:value for money

[ticktickboom]

is there any sort of graph or table which depicts the amount of break horse power added by various modifications and these positioned against the cost involved?

ergo determining what modifications are most value for money?

[Shug]

Lol

No - fraid not.

Plus, BHP isnt like a bolt on - a freer flowing filter will add a couple of horsepower at best to a standard engine, but might add 10 to one with hotter cams/better breathing where the filter is a restriction. You have to look at horsepower mods as a holistic thing, not on a part-by-part basis. Plus, there are many ways to arrive at horsepower figures that will feel very different. You could make 150bhp on a standard K series by whacking in a set of cams, or by doing head porting and bigger valves. One will produce the power in a more torquey fashion, one will just make it rev better and get the power through revs (simplistically) Afterall, BHP = (rpm x torque) / 5252. You can change different things in that calculation to end up at the same result.

Anyway, you want the car to be faster, the first thing you change are the suspension and brakes for track. Or driver training to be quicker yourself - a lot of Elise 'straightline speed' is more to do with corner exit than horsepower.

(having spent thousands - sometimes up blind alleys - on every kind of mod over the last 6 years, I feel qualified to comment )

[ticktickboom]

cheers!

[Shug]

Realistically, what you want to do is ask what you want to spend and what you want to achieve.

You'll get a lot of constructive advice if you go down that path mate

[Mike Scib]

What are the options/benifits/costs when modding a K-series?, i know the old school know the answers but others don't.

[Shug]

Big topic...

Firstly - any time you mod a K, the possibility of less reliability crops up - has to be said.

Also assuming things like Exhausts are chosen to compliment the work. I'm not going to list stupid things like air filters and backboxes as you'll probably get more horsepower difference running on a colder day - but they're worth it for removing choke points for future mods

I suppose phase one would be either headwork or cams you could get up to the 150/160bhp bracket with that. Retains standard ECU - maybe looking in the under £1000 bracket (less if you can source the bits cheap and do it yourself)

Next would either uprate cams & go to harder springs etc (if you'd already done the headwork) complete with ECU and DTHTBs. Another £1500 for this lot + mapping. Looking around the 175-190bhp bracket. For longevity with this, you'd want forged pistons as well (around a grand) - standards aren't much cop over 170bhp, but some take the risk.

Next step would be going proper ported VVC or VHPD head with bigger valves - solid cams. 200+ BHP, forged pistons essential, plus better looking in more detail at the bottom end. Cost as much as you want it to - realistically not much change off £2k (plus the ECU, Exhaust, TBs, etc that you'd already have bought earlier in the process)

Then, go mental with a 1.9 Scholar bottom end (all steel & balanced somewhere like Vibration Free) - go chasing 250bhp and a new mortgage.

That's really really rough ballparks and ignores things like uprating alternators if you rev it past 7.5K, CR gearboxes, which are essential when you start chasing HP through revs, etc, etc.

No such thing as cheap horsepower - no matter what the snake oil salesmen say. It's at this stage that the engine swap prices stop looking as silly - especially when you consider a 200bhp K series is a pretty highly strung beastie that will need rebuilt every 30k miles or so to keep it A1.

lots more info at http://www.dvapower.co.uk

[Mike Scib]

Cheers Shug

[Rich H]

CR box: get to 90mph faster then run out of puff...
(That's puff not poof, unless it's an S2 )

[philthy]

the CR box really isnt that short, esp compared to a Honda 6 Speed!

[Mike Scib]

the CR box really isnt that short, esp compared to a Honda 6 Speed!

A Honda CTR box? Good for 145mph in a EP3, or are they modded before fitting to a Elise?

[steve_weegie]

the CR box really isnt that short, esp compared to a Honda 6 Speed!

A Honda CTR box? Good for 145mph in a EP3, or are they modded before fitting to a Elise?

Sounds about the same as the CR elise box, which is hitting a smidge over 140 @ 7000 rpm... Guess the CTR is slightly shorter but revs higher?

[philthy]

IIRC the UK civic K20 box is good for 170 at the top of 6th.

The difference around knockhill with the 2 boxes is night and day.

[Mikie711]

(having spent thousands - sometimes up blind alleys - on every kind of mod over the last 6 years, I feel qualified to comment )

Here here, and as I am in the middle of doing the same I have to agree with Shug, however his prices are conservative.

[robin]

Difference between boxes is easy to calculate with the aid of a spread sheet or a wee program. There is a spreadsheet on the internet called "cascade" or something like that (so named, perhaps, because the graphs look like cascading water falls).

A close ratio box wins over a longer ratio box by allowing you to use a narrow band of revs that maximises the power generated by the engine at all times. This is commonly known as "maximising the area under the curve."

If your engine produces a flat power curve - not many do, but it might happen artificially, e.g. for use in class A of the LOTRDC where the 170 BHP limit can be maintained across as wide a rev range as you like and you may consider the bottom end expendable so have a fairly high rev limit - then the shorter ratios might not win significantly.

OTOH, if your engine has a peaky curve (like anything making more than 190 out of the 1.8 will probably have) then you need the closer ratios to stay out of the dead zone "off cam".

Comparing the standard S1-type "long box" with the standard S2-type "short box" (ignoring VVC S2 that has a different set of ratios) I would say it's generally not a huge difference for K-series engines < 170BHP and the difference isn't really pronounced until you hit around 190BHP, normally aspirated.

The "short box" has a significant disadvantage when it comes to motorway cruising and fuel economy, though (I'm lucky to get 38mpg on a run up the A90 with the close ratio box, whereas I think with the long box you can make 45mpg on similar runs at similar speeds).

I'm just waiting for my bottom end to go bang - then I'll decide on fitting either the standard long type (I've got one lying around) or the S2 VVC type (unpopular weird ratios, but actually good for track and cruise, provided you're up for thrashing the living daylights out of your car in 2nd gear on track ).

Cheers,
Robin

[Shug]

(having spent thousands - sometimes up blind alleys - on every kind of mod over the last 6 years, I feel qualified to comment )

Here here, and as I am in the middle of doing the same I have to agree with Shug, however his prices are conservative.

Aye - have to stress, very rough figs off the top of my head, not including exhaust manifolds or airbox setups, or the thousand little niggly things like FPRs injectors, oil pumps, yadda yadda... So yeah, in hindsight, the prices have little margin in them (and they are to upgrade from the last stage, not do it from scratch each time) Plus it's been a few years since I looked at it in any serious way WRT costs