[na8cgee]

Hi,

a little bit of background information first!

I have a roadrunner sr2, which is basically a caterham 7 replica which runs the mazda mx5 running gear (Rear diff / gearbox / BP engine). When I first purchased the car, it had a standalone ECU and made approximately 145bhp/130ftlb. This was achieved with a 1995 1.8 block which is around 9-9.5.1 compression and everything else was stock.

The car itself is a great drive but I always wanted that little bit more power as the chassis can certainly take it/begs for more power on the longer tracks.

So after this point the new engine build started!

After various research and reading Quinns thread on miata.net (just search 185whp miata in google if you want a good read). I decided on the following basic spec, i will go into more detail further on in the thread:

- Canems ECU (Full sequential)
- mk2.5 1.8 VVT stock bottom end (10.1 CR pistons)
- mk2 BP4W cylinder head
- custom camshafts
- Jenvey throttle bodies
- mk2.5 1.8 VVT injectors (265cc) with a tomei AFPR set to 4 bar static (58-60 psi) & walboro 255hp fuel pump
- Custom exhaust manifold
- Shortened & baffled sump (Increase oil quantity as well if possible)
- Aiming to tune on 95 ron (91 octane in america)

Bottom end

So the bottom end was sourced from a wrecked SVT sport on Ebay. Initial visual inspection looked good and using plastigauge I checked the rod/main bearings and they were all within clearance so it was all re-torqued up and it was ready to go. Not really much to say in this section but thats the beauty about it, very similar and cost effective to replace If I damage it in the future.

BP4W cylinder head

This cylinder head was chosen due to its ability to flow good CFM and its improved port angle on the inlet side. I sourced a BP4W from Ebay, it had been through a rough life with lots of carbon build up and the valve guides were well out of spec when inspected.

The cylinder head was fully stripped down and the porting process began, I won't go into too much detail here as I took many measurements/documented my work in another thread on here: http://www.mx5nutz.com/forum/index.php?showtopic=324810&page=1

The cylinder head was then sent to stanwood engineering, a local engine building shop near to me, where they replaced all the valve guides, installed my new VS855 valve springs/Camshafts/SUB lifters/set correct lash etc Stanwood also provided 5 angle valve seat cuts on both intake and exhaust, this significantly improved the low lift flow rates. (originally I was going to go for 3 angle but they persuaded me!)

After much debate I originally was going to skim the head 60 thou as per Quinns thread, but decided against that due to wanting to utilize 95 Ron fuel so this was limited to 0.30 thou.

I ended up with the head flowing 217CFM Inlet at 0.4" valve lift and 205CFM exhaust at 0.4" lift.

Custom camshafts

So the camshafts were a bit of an unknown to me (I still don't 100% understand them yet either!) but I took advise from various places in terms what is better? a high duration/high lift cam or a low duration/high lift cam etc etc

In the end seeing Quinns results, I knew his cams had 10mm of lift and were 264 advertised duration. I started to work with Justin at Piper cams to develop a camshaft that was quite aggressive off the seat so that it opened the valve as quickly as possible to get into the high CFM regions of the cylinder head flow rates. After a few weeks of bouncing E-mails we came up with the 264 degree camshaft, 10mm max lift with 44 degrees of total overlap, the LSA of these cams is 110. The full cam spec sheet is posted in the cylinder head thread if you wish to see it.

These camshafts required the use of mechanical lifters, I used mazda motorsport SUB lifters from miataroadster.net - great international delivery speed and good customer service! also, to provide the cams more valve control I upgrade the valve springs to VS855, These valve springs can cope with a max total lift of 10.3mm and are substantially stronger than the OEM units. Maruha states that the OEM springs are suitable for 10mm of valve lift, but when we tested my old valve springs from a NA8C mx5, they were too tired/used and didn't have enough pressure. The VS855 valve springs work perfectly with the OEM retainers.

Jenvey throttle bodies

I knew I wanted to use ITB's because it would allow me to tune the inlet runner length to suit where I wanted my powerband to be. I had the choice between a DanST motorbike ITB kit and Jenveys. In the end I chose Jenvey throttle bodies, the only reason being they look great and I could attain the ITB size I needed for my application easily.

The main difference between my setup and the normal jenvey kit is that I have chosen to use 42mm ITB rather than 45mm ITB. why would you do that? I get this question alot at the moment, and its purely down to the max CFM required for my application. a 42mm ITB can flow approximately 300CFM, more than my engine can accept at any stage as I am limiting my engine to 217CFM due to max camshaft lift at 10mm/0.4".

The next question is usually, if thats the case then why do Jenvey sell the kit with 45mm and not 42mm? In my opinion, they are two things by selling the 45mm in the kit. The first being they want to move the effective powerband of the engine up the RPM range (By increasing the area of the inlet tract you move the powerband up the RPM, this is due to the air speed inside the inlet tract taking longer to pickup speed due to the larger area) secondly, they want to ensure that the customer is making max power at the stock RPM limit rather being at the aboslute limit of the ITB diameter at the limiter.

If you look at Quinns thread where he shows various states of tune for his engine, including going from various ITB diameters and finally ending up at 50mm (!). 50mm ITBs are seriously big and you can see how the engine lost a lot of low/mid RPM air speed which caused the torque to drop off but increase the top end torque due to less physical restriction in the lnlet tract.

In this application, the 42mm ITBs are maxed out to provide the best spread of power between 3000rpm-7000rpm. anything beyond this RPM range and the engine is out of its efficiency zone ( volumetric efficiency) and torque suffers as a consequence.

The inlet length of these ITBs has been specifically tuned to camshaft specification and to make use of the 3rd & 4th harmonics in the inlet tract. This can be seen in the dyno graph where the torque of the engine is significantly increased between 5000-7000rpm because the inlet length is tuned to provide harmonic assistance to the air charge (Positive pressure can be seen on the MAP sensor around 6000rpm), thereby increasing the engines VE ratio.

In this instance the inlet system is tuned to provide 3rd harmonic benefit between 5500-6600rpm

Fuel system

The fuel system is fairly basic on this setup, the cylinder head injector ports have been blocked on and the jenvey ITB injector boss locations have been used, this is to aid with fuel/air mixing before it enters the chamber. The injectors are 'purple' 265cc mx5 01-05 but a tomei AFPR set to 60psi static pressure to provide approximately 300cc equivalent injector size, the slightly higher fuel pressure also assists in fuel atomizing in the inlet tract, but only a small benefit at this pressure level. a walboro 255hp fuel pump provides the required fuel delivery rate.

Custom exhaust manifold

This is where things get very interesting because the exhaust manifold, in this application, is what literally makes the engine so great. You can perform many calculations which tell you the ideal inside diameter of the primary tubes, the ideal length of the primary tubes for a given RPM range and the required collector length/exit diameter. These calculations also take into account the camshafts as timed in the engine because the exhaust valve closing/opening points dictate when exhaust scavenging is going to be at its most effective.

First to look at the primary tubes inside diameter, this figure is critical to how the engine operates/feels. Go too small on the primary tube and the car will have incredible low down torque but will be significantly restricted at the top end. Go too big on the primary tube and the exhaust gas will never reach peak velocity which is where peak scavenging takes place and you won't see any benefit to 'tuning' the exhaust per se.

All my calculations are located on my build thread but basically the ideal primary tube inside diameter for a stock RPM, 83mm BP engine is around 1.52-1.55" ID (38.6mm - 39.3mm). This primary tube inside diameter ensures that the engine is not restricted from a flow perspective a the top end of the RPM range but provides the best scavenging effect at the tuned length of the exhaust manifold itself.

I proved the above theory by mistake whereby the first exhaust I had built was the correct length but was built with 1.5" OD (38mm) exhaust tube which was basically 1.38" ID (35mm). as you can see on the dyno chart, the engine made fantastic low RPM torque due to the increased exhaust velocity but it couldn't breathe effectively past 6000rpm.

The length of the manifold dictates when the peak scavenging effect occurs, in my case I tuned the exhaust for 5000rpm which you can see on the dyno chart of the solid lines that the torque increase is impressive, which is basically the exhaust manifold assisting with the removal of exhaust gasses from the cylinder by using a slight vacuum placed on the back of the exhaust valve at that particular RPM point.

Here's a lovely picture of the finished article:

Shortened & Baffled sump

The sump was shortened, and the oil pickup as well due to needing increased ground clearance (speed bumps & aluminium sumps do not make best of friends at speed!). I also created/installed some baffles with viton rubber gates to hopefully control the oil during trackdays. The oil capacity of the sump was increased to 5L as well just for peace of mind.

So the good bit, this is the dyno plot for the car. What is amazing to me is that the dotted line is the smaller diameter exhaust manifold and the solid lines is the correct diameter as detailed above. Why bother buying a camshaft for a particular application when you can manipulate the engine's characteristics with a difference exhaust manifold!

In the end she made 198bhp at 6740rpm / 162ftlb at 5570rpm.

The dyno run was performed in 4th gear, starting at 2600rpm upto 7400rpm but stopped recording past 7218rpm due to not making any more power.

Dyno feedback

As you can imagine myself/Dave (Canems ECU tuner) were amazed as to how much power we had released at the top end whilst only loosing 10-12ftlb between 3500-4500rpm. The setup was never going to release anymore power, rather it was just moving the VE efficiency point from left to right on the chart. The interesting point is that the exhaust is no longer the limiting factor on this setup, its the 42mm ITBs.

the 42mm ITBs, with the boost from the harmonic tuning between 5500-6600rpm, are pretty much on their limit at 7000rpm. This is mainly due to the high RPMs of the engine and the fact the induction length is fairly long which introduces a lot of frictional losses.

The only interesting, and slightly annoying point, is that this engine is timing limited because of the 95 ron fuel (91 USA). I thought by going conservative with the CR I could reach MBT on 95 but the mid range dip on the dyno graph is where we had to pull significant engine timing (Which makes sense because if its going to pre-detonate it would be a high load/low RPM events).

This leaves a really important question of: How much timing could we gain on 99 ron fuel (93 USA) ? According to Quinn's build we should easily reach MBT with our predicted 10.8 CR, which would really fatten up the torque curve down low and maybe carry a few more BHPs at the top end? At this stage i'm not 100% sure but It's becoming an Itch I want to scratch to see how much benefit some additional timing in the engine will effect the power curve.

Overall though, the new engine setup has made the 600kg full wet weight car a real blast to drive at circa 325bhp per tonne

Any questions just ask, I will have missed out on many things I'm sure!

 

[Shadowraven]

So very crudely... 0.30 thou skim, 45mm ITBs, 10mm 264 degree cams and a manifold saw you hit 200bhp? That seems impressive. May I be so crude as to ask what cost was involved in making that power? And how reliable it is, Quinns is meant to be reliable isn't it?

 

[Thruxton]

Great write up and a fantastic result.
Thank you for all the details and sharing this build.

Regards.
Rich

 

[mbh69]

I have a blink stage 2 power upgrade and mk2.5 vvt bottom end, I made 181.5bhp on efi parts dyno similar engine spec.

 

[na8cgee]

So very crudely... 0.30 thou skim, 45mm ITBs, 10mm 264 degree cams and a manifold saw you hit 200bhp? That seems impressive. May I be so crude as to ask what cost was involved in making that power? And how reliable it is, Quinns is meant to be reliable isn't it?

As a basic list:

- 10.1 CR bottom end (2001-2005 mx5)

- bp4w cylinder head, ported, 5 angle valve seats skimmed 0.30 thou (estimated 10.8 CR)

- 42mm Jenvey throttle bodies, total inlet tract length of 355mm (Critical for power boost tuning of the intake at 5500-6600rpm)

- Custom exhaust manifold, 4-1 style with 1.53" ID primary tubes, 2.5" V-band outlet with full 2.5" exhaust

- 264 degree, 10mm lift cams, 44 degrees overlap VS-855 valve springs

those are basically what allows the power to be achieved. the above is a horribly crude list though because if you were to just slap all the above setup together and not consider inlet/exhaust length and Internal diameter tuning it wouldn't perform as it has. For example, if the inlet length was not tuned in partnership with the exhaust length, I don't think we would have seen the jump up in torque past 5000rpm and as such it would have only made approx 140ftlb / 175 bhp at the same RPM points.

Cost wise is difficult to make an accurate figure because Its hard to put a price on the amount of my man hours involved but a good guess without my time costs involved would be around £3000 from start to finish (no engine to fully built/dyno tuned/making power).

Reliability is an interesting one because I am making this power within the OEM rev limits effectively, only using the additional 7400rpm for gearing purposes (When I change gear with the 5 speed, it drops me perfectly into the powerband when shifting between 7000-7400rpm). The additional compression within the engine will be giving the piston rings some more stress but it should be fairly reliable *touches wood*. As with anything though only time will tell if the engine proves to hold itself together, In my opinion i think it will be just fine.

I believe Quinn has done many a trackday with his current 185whp setup without any major issues, considering that engine has significant compression changes that would be the engine to show any issues first if we are to see any.

Just out of interest, on this current setup if I was to change the 42mm ITB to the standard 45mm ITB as per Jenvey's standard kit, the calculations suggest that the powerband would effectively move 400rpm to the right (Higher up the rev range), the only downside to this would be the low end torque would suffer as a consequence due to lower air speeds at those RPMs.

The question I keep asking myself is - do I need another 5-10ftlb past 5500rpm at the expense of 5-10ftlb below 5000rpm?

At this point probably not, 130ftlb at 3000rpm is very nice when cruising around on the road.

 

[Shadowraven]

Hmmm, very interesting. I only ask as I have a track car which I'm trying to decide what the power goals should be on, I don't like the parasitic lag of a super charger and was considering a simple td04 set up but don't really want all the additional heat and turbo surge for track. I didn't think 200bhp was attainable for a stock BP engine and Quinns 185bhp build seemed to cost a huge amount (but he did buy stuff like a very rare and expensive header). I may reconsider looking at this.

A quick question about the heads, everyone seems to want the mk2 head (98-00). What was changed from 2001 that makes these not as suitable?

 

[jon]

A quick question about the heads, everyone seems to want the mk2 head (98-00). What was changed from 2001 that makes these not as suitable?

VVT. Which is actually good, if you have an ECU that can control it.

 

[Shadowraven]

A quick question about the heads, everyone seems to want the mk2 head (98-00). What was changed from 2001 that makes these not as suitable?

VVT. Which is actually good, if you have an ECU that can control it.

Ok, I did suspect it was a complexity thing. I couldn't find any reference to actual changes in the head design. Do correct me if I am wrong though.

 

[jon]

I think the basic design is the same apart from the VVT gubbins on the inlet - it'll all still bolt up to an earlier 1.8 block, mk2.x inlet manifold and mk1 or mk2.x exhaust manifold. I've read somewhere that the inlet cam is a lot more aggressive than the earlier ones too.

 

[R3k1355]

That exhaust manifold looks ace.

So it effectively gave you nearly 40hp over the other one?

 

[Fercho]

Wow superimpresive!

Thanks for amazing write up!

Which megasquirt are you using? Can you post AFR and ignition tables?

 

[Dickie]

Just a note to add to the excellent post.

Fantastic power to weight ratio.

Back in the day 100 Bhp per ton was a good enough for racing.

The Mk 2 Head has more aftermarket camshaft choice which is why a few of us are using it. ( As has the Mk1 Head )

The inlet ports are higher than the Mk 1 which may or may not be an advantage.

I am sure a few good regrinds will appear for the VVT head at some point.

 

[LukaGt]

im also runnig similiar setup

vvt block

vvt head

4-2-1 header

jenvey 45 mm itb

cat cams

made 182hp and 195 nm

 

[na8cgee]

That exhaust manifold looks ace.

So it effectively gave you nearly 40hp over the other one?

It's crazy to say but yes, the only difference between the two power curves is a 3mm increase of primary tube internal diameter!

(Obviously we optimised the AFR/Timing for both exhaust diameters)

After checking over my notes I am going to try some different cam timings on the inlet size (I only played with the exhaust on the first, smaller exhaust dyno but not cam timing change for the bigger diameter) which will either smooth out the bottom end dip or will completely kill the power across the Rev range (due to changing the engine's effective dynamic compression). This means back to the dyno so I'll need to book some more time!

Just to keep this thread somewhat updated, the car has ran flawlessly for the last few months, being beaten on in 25 degree weather with no issues. I really need to get a go pro/action camera because the way the engine picks up past 5000rpm is really addictive, I can only describe it as a vtec like effect lol. It certainly makes me giggle every time I drive it.

On a side note, using some engine analyser software from a friend in the motorsport industry we tried out a larger ITB diameter simulation to 45mm. To estimate what could potentially happen, assuming no other restrictions are present than the known ones the software indicates 214bhp at 7500rpm and 166ftlb at 6400rpm as max theoretical values.

Personally I think those figures are very optimistic and I would be surprised if we got over 210bhp, more like 205-208bhp at a guess with some torque loss down low.

The only problem is I contacted jenvey to ask for a cost to bore out my 42mm's to 45mm but they just said they don't do it buy a new set for £500... not great!

Might need to get creative with a local machinist & a decent lathe!

I run a canems ECU and yes I'll certainly be happy to post AFR targets (although I can tell you at full load we're aiming for 12.5afr)

Timing map wise I'm always a bit nervous posting these because (no offence intended) I wouldn't want someone to just use those figures in their engine and expect it to be ok/potentially do some damage because as I'm sure your well aware that every engine prefers different timing figures.

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[R3k1355]

Timing map wise I'm always a bit nervous posting these because (no offence intended) I wouldn't want someone to just use those figures in their engine and expect it to be ok/potentially do some damage because as I'm sure your well aware that every engine prefers different timing figures.

As long as it's made clear it's not a good idea then there's no real issue.

No sensible person would just blindly stick on another timing settings anyway.

 

[na8cgee]

Ok so here's my timing map for the current tune, please be aware this timing map is my car specific and will most likely not be optimal for yours!

https://uploads.tapatalk-cdn.com/20180610/2bddbb0a9bccc790a5f84b726cff9d6b.heic

I'm running a very 'safe' timing map apart from the 2500-4000rpm region where we were having to pull timing fairly significantly - I think this was due to on using 95 Ron fuel and approx 10.6-10.8.1 CR.

Judging by our friends over the pond, they are running 32-36 degrees advance on 93 Oct so there's probably some power to be had in changing fuel grade.

I have tried a few tanks of shell V-Power recently (99 Ron) and as expected it is a lot happier/smoother in bottom area of the Rev range (although this could just be perceived).

I still there's more to be had in the cam timing, not necessarily peak but a flatter torque curve, I am going to try that as well once I get to the dyno!

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[R3k1355]

Judging by our friends over the pond, they are running 32-36 degrees advance on 93 Oct so there's probably some power to be had in changing fuel grade.

Don't they use a different measure of Octane rating to us though?

So when they say 91/93 Octane it's actually not lower than our 95 Ron stuff.

 

[na8cgee]

If a fuel is 98 RON then it will be 93 PON - 93 PUMP GAS

If a fuel is 95 RON and 87 MON then it will be 91 PON -> 91 PUMP GAS

hope this helps (it can get confusing!)

Basically this car is currently tuned for 91 pump gas (95 Ron) at this time, but I'm looking to tune to 98/99 Ron which is 93 pump gas

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[oceanson]

Great job! nothing like the crisp feeling of a Na engine

 

[na8cgee]

Just got back from another 3 hours on the dyno, trying out some new cam timing settings and also tidying up the fuel maps.

We did power runs at each cam setting so you can see how the engine responds.

No graphs yet as I'll get them through E-mail probably tomorrow/Friday but just as a teaser, the final power run is comfortably over 200bhp

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