How many RWKW do you have with what mods?

[rascal]

Old motor 174rwkw.

New motor with way more mods and 150rwkw feels way quicker.

Which also makes the excellent point that peak power is not everything....

[Magpie]

I have always liked this post http://forum.miata.net/vb/showpost.php?p=5704021&postcount=24. Whilst it is American and for natural aspirated builds it asks some good questions.

Personally, I prefer to ask the question do you want straight line speed or do you want to corner? The motto for a drag racer is if you can corner you are going too slow.

Also a dyno is good to measure change, hence the requirement to use the same dyno. Dyno shopping is not a good idea.

Decide on a few things up front and it'll be easier for the rest of us to offer useful advice.

-Autocross, what class?
-Wheel to wheel racing or HPDE only, what class?
-Street only?
-Does it need to be emissions legal in any state? (what state)
-Must it be able to run on pump gas and if so, what octane?
-Must it run in a street car, (A/C, OEM alternator, col start driveability etc) ?
-Actual budget for everything connected to engine/power making hardware?
-Tuned by a pro or semi-knowledgeable amateur?
-You cool with the additional tuning/set up hassles of an IRTB set up?
-Does the car need to be quiet?
-Do you have a shop in mind that is familiar with race BP series builds?

Cost no object, I suspect someone could build a 300whp grenade that runs on exotic fuel. In the real world 150-190whp is doable within the budget of the most of us.

150whp is bolt-ons and a good tune. Above that you need to go into the motor.
160-165whp is just a little bowl work and compression.
170whp requires more substantial head work or mild cams or lots of compression, pick one.
185whp requires mild cams (still streetable in a VVT), compression, porting. Pick two.
195whp full head work, lots of compression and mild to medium race cams.
205whp+ is pretty much a full race engine with cams that would probably never idle for street use.
225whp+ so and the life expectancy begins to shorten. Perhaps 15-30 race hrs and you're looking at a $15-20K long block.

We have just touched 180whp on stock cams with an NB2 motor but it was not cheap. Based on the data from that experiment, I know 190whp on stock cams is possible with IRTB's, more compression and E85. At that point however, you should just feed it the cams it wants. We played with stock cams to gain a higher BFSC for endurance racing.

For most guys, I think a stock-ish cam NB2 build makes the most sense. Run as much compression as your fuel will stand, get the best ECU you can, build a Honda B series manifold grafted onto the Mazda flange, RB/Maruha/Maxim works header, fully port and polish the head. Forged everything, SUB's and heavier valve springs. That should net and easy 175whp or so, be safe to 8000rpm sustained, idle like a stocker and last 100 race hours.

[rascal]

^^^ is a great post, though being American you need to subtract 30 from each of the figures to match Aussie dyno HP figures. (ie just bolt-ons and a good tune is more like 120hp in Oz)

[kazama]

i dont understand?
why subtract 30?

[rascal]

Cos American dynos must calculate hp differently to aussie dynos.

ie first example - bolts-ons and tune = 150hp. This combination on an aussie dyno shows more like 120hp at best rather than 150.

Also I hope to soon have the 185hp combination and would expect to see about 155hp on aussie dyno.

[Magpie]

rascal is correct my build gave 182 HP (GT Auto hub dyno) and it has ITB's, 85mm bore, medium race cams, 11:1 compression, serious head work.

Notwithstanding it is a well thought out post and not too many people have disputed the information in it (with the exception of the quoted horsepower figures). The real information is in the % increase as you make changes. For example going from the 150 to the 195 suggestion represents a 30% increase in power, this is about right!

[johnnyreble]

well I bolted FFS supercharger on stock 1.6 NA and got 158rwhp on the dyno in Aus'
But as has been pointed out Dyno's vary....

[taminga16]

Taking in to account the OP's goals, if the results were viewed as percentage gains for each mod, would it really matter what individual Dyno's displayed? (as long as the before and afters' were created on the same machines).
Greg.

[Magpie]

taminga16 correct. He should get a baseline dyno test and then a final one, from the SAME dyno.

[bruce]

OP has just rehashed the repeated question - what mods have you done? Answered ad-nauseum over the years.

[plohl]

dyno chart by plohl, on Flickr

Before and after adding cams and re-tune.

Netted ~20% increase in peak power, 131whp (97rwkw) vs 109whp (81rwkw) and ~11% increase in peak torque. You can see from the graph, torque increase over the whole rev range.

My new car has ~100hp, however I do not notice a great difference between them. I think this is due to the lightened flywheel/clutch assembly in the new car.

Vmax at lakeside in the previous car was ~180km/h; new car ~170km/h.

Old car PB: 65.9s; New car PB: 64.8s.

Same tyres, similar conditions and suspension set ups.

[pcmx5]

My figures are all from Dyno Dynamics dyno's and they showed remarkable consistency over a range of cars at Vic Club Dyno days(Caulfield Jag) Maztech and Dalton Automotive.

Standard NA8A with Genie catback 66RWKW; with CAI extractors , Town and Country exhaust high flow cat. and Malpassi fuel reg 74 RWKW;as before plus Tighe 805c cams and Microtech 94 Rwkw; after engine rebuild new rings ,bearings (standard) head reco port and polish and bigger exhaust valves 102 RWKW.

Peter.

[speed]

Thank you all for your input.
Apologies for not replying with individual quotes. Not so easy on the phone.
% or dyno figures give me the ballpark figures that I'm looking for. My only issue with % is that they are calculated correctly and I don't expect peeps to do that. Ie i thought 150 to 195 is 23% not 30. Maybe I stuffed up.
Also agree that peak power is not a fair indicator on performance but thought many of you have been to dynos and it is a figure all the same.
My over all intention was to gather your results and have it sticky'd so future noobs like me could see it in one place and not have to repeat the usual posts. I'm trying to help so I apologise if such a repeated post offends you.
Some of you have some awesome rides and power figures. Seems 80+Kw atw is pretty awesome in a n/a.
There also appears to be a variety of preferences to get the desired power. Turbo, supercharged, cams etc.
Not all of us want the highest power figure on the block. I personally want to keep mine n/a, sorry dan but I just don't need another turbocharged car, although I do agree turbo is the best bang for buck approach.
Maybe there should be a sticky for N/A power mods and a separate sticky for F/I power mods?
Personally mine is a streeter that I may take to the track for a couple of meets. Drivability on the street is paramount for me.
Pls feel free to add your stats and mods. Before and after results are awesome.

There must be other noobs out there that want power mods confirmed by (and i steal this phrasing from dan) someone who has very little conflict of interest. So please keep the posts coming


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[Magpie]

I agree on a Natural Aspirated section, but I'm biased!

This is why I love numbers, they can be manipulated! The 30% was achieved by:

From 150 to 195 is 45. Therefore to increase from 150 to 195 is 30% (45/150).

Keep asking questions, it is the only way to learn. However the search function can turn up some of the answers. There are a few people on here that have built non forced induction MX5's and would welcome another person to the dark side (empty bank account side).

Good luck with your build.

[ralt]

Hi.
If you are going to produce more power and use it on the street you can get good results with modest outlays.
Have a look in the dyno section to see my results.
The most important key is the same with any modified engine the cylinder head. Tread carefully with this there are many people who make lots of claims but are usually short on results. Go to a race meeting speak to people who use these cars and ask who does their heads or send me a pm for my head man who uses a flow bench and is not expensive really knows his craft. Its what got my results.
I could go on and I guess you want to know how much?
$3500 which includes $800 for a low km replacement engine.
Enjoy your journey. Terry.