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Ok somehow I've stopped getting updates from this thread, just had to big it out for someone on FB, I'm glad to see it's still going. Interested to see that graph.
1.8 Mx5 Na Power Build, Stock Bottom End - Overview / Thoughts
21 - 38 of 38 Posts
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So I decided to head back to the dyno, with the following changes from the last dyno:
- fresh oil/filter (5w40)
- fresh Spark plugs (modified earth electrode and indexed)
- shell V-power nitro fuel (99ron / 93oct)
- repaired the throttle cable!
So we strapped the car down, did a quick power run to see if we still matched power wise, it came back at 167bhp..... after reviewing the chart we realised we were really rich AFR throughout the range, this is when we realised the throttle plates we only opening 65-70%!
So we repaired the throttle cable (it must have stretched with use, needed to adjust my pedal stop!)
The car then pulled 201bhp on the same map, happy days - well within the last dyno results, I also adjusted the throttle linkage and I think we gained a bit more flow through the throttles because we had to add fuel throughout the range! Once this was sorted we started to play with cam timing.
The previous mapping session/dyno left the inlet cam 'straight up' which is as per the cam card but I had the exhaust cam retarded 2 degrees. So we put the exhaust cam back to 'straight up'
https://uploads.tapatalk-cdn.com/20180622/5810433b674e1108ad998afc3c4bfbc9.bmp
So the cams straight up made the power pretty well, although the torque curve past 6000rpm dropped very fast compared to the previous 198bhp dyno. The main plus with moving the exhaust cam back to straight up meant we gained some dynamic compression which helped the torque around 4000rpm by around 3-4ftlb, but as the car is fairly lightweight we didn't need it there!
So the next trial was to go the other way and retard the exhaust cam by 4 degrees (2more degrees than the 198bhp run).
https://uploads.tapatalk-cdn.com/20180622/c4194712825fbb74b3d87d3527374dee.bmp
As you can see the car didn't like that at all! Power down throughout the range, we suspected this was because we lost a significant amount of dynamic compression which would explain the lack of power everywhere!
So after a few more settings we trialed (with no reason to show the dyno chart) the best setting we found was inlet cam straight up and the exhaust cam retarded 1.5 degrees - this was the best balance between top end power and retaining the dynamic compression to improve torque.
So final results after optimising the AFR's (we ran slightly leaner at 12.7-13 AFR due to the better fuel giving us more confidence) and massaging the timing map, the results were in:
https://uploads.tapatalk-cdn.com/20180622/9a3ef88603708584480a5c3db3748f9e.bmp
211bhp / 172ftlb
As you could guess I am pretty excited about these results, mainly because the dyno used was the same with the same tyre pressures and correction factors so the additional changes/can timing changes gained 12-13bhp - well worth the faffing on the dyno!
I'll post the video of the 211bhp pull soon, we did see a highest reading of 216bhp but this was when the engine was allowed to cool off, 211bhp is the more accurate result as the engine was heat soaked by this point (back to back runs to prove output).
There's definitely no more to be had on this setup - we hit MBT in every cell at WOT, to prove this we advanced the timing by 2 degrees across the whole map just to see what would happen:
https://uploads.tapatalk-cdn.com/20180622/0762f16e792b08a1b37f41ba31106409.bmp
We never suffered any knock during the tuning, so this compression ratio and 99ron is good setup BUT the compression ratio was 'just' enough for these cams, this can be seen by the 4 degrees retarded dyno chart, just bleeding off a little bit more compression dropped power everywhere.
Driving the car is just fantastic, I love how the power holds to the redline stronger now.
Another cool thing is the power to weight ratio is approximately 350bhp/ton - it's great fun!
Sent from my iPhone using Tapatalk
- fresh oil/filter (5w40)
- fresh Spark plugs (modified earth electrode and indexed)
- shell V-power nitro fuel (99ron / 93oct)
- repaired the throttle cable!
So we strapped the car down, did a quick power run to see if we still matched power wise, it came back at 167bhp..... after reviewing the chart we realised we were really rich AFR throughout the range, this is when we realised the throttle plates we only opening 65-70%!
So we repaired the throttle cable (it must have stretched with use, needed to adjust my pedal stop!)
The car then pulled 201bhp on the same map, happy days - well within the last dyno results, I also adjusted the throttle linkage and I think we gained a bit more flow through the throttles because we had to add fuel throughout the range! Once this was sorted we started to play with cam timing.
The previous mapping session/dyno left the inlet cam 'straight up' which is as per the cam card but I had the exhaust cam retarded 2 degrees. So we put the exhaust cam back to 'straight up'
https://uploads.tapatalk-cdn.com/20180622/5810433b674e1108ad998afc3c4bfbc9.bmp
So the cams straight up made the power pretty well, although the torque curve past 6000rpm dropped very fast compared to the previous 198bhp dyno. The main plus with moving the exhaust cam back to straight up meant we gained some dynamic compression which helped the torque around 4000rpm by around 3-4ftlb, but as the car is fairly lightweight we didn't need it there!
So the next trial was to go the other way and retard the exhaust cam by 4 degrees (2more degrees than the 198bhp run).
https://uploads.tapatalk-cdn.com/20180622/c4194712825fbb74b3d87d3527374dee.bmp
As you can see the car didn't like that at all! Power down throughout the range, we suspected this was because we lost a significant amount of dynamic compression which would explain the lack of power everywhere!
So after a few more settings we trialed (with no reason to show the dyno chart) the best setting we found was inlet cam straight up and the exhaust cam retarded 1.5 degrees - this was the best balance between top end power and retaining the dynamic compression to improve torque.
So final results after optimising the AFR's (we ran slightly leaner at 12.7-13 AFR due to the better fuel giving us more confidence) and massaging the timing map, the results were in:
https://uploads.tapatalk-cdn.com/20180622/9a3ef88603708584480a5c3db3748f9e.bmp
211bhp / 172ftlb
As you could guess I am pretty excited about these results, mainly because the dyno used was the same with the same tyre pressures and correction factors so the additional changes/can timing changes gained 12-13bhp - well worth the faffing on the dyno!
I'll post the video of the 211bhp pull soon, we did see a highest reading of 216bhp but this was when the engine was allowed to cool off, 211bhp is the more accurate result as the engine was heat soaked by this point (back to back runs to prove output).
There's definitely no more to be had on this setup - we hit MBT in every cell at WOT, to prove this we advanced the timing by 2 degrees across the whole map just to see what would happen:
https://uploads.tapatalk-cdn.com/20180622/0762f16e792b08a1b37f41ba31106409.bmp
We never suffered any knock during the tuning, so this compression ratio and 99ron is good setup BUT the compression ratio was 'just' enough for these cams, this can be seen by the 4 degrees retarded dyno chart, just bleeding off a little bit more compression dropped power everywhere.
Driving the car is just fantastic, I love how the power holds to the redline stronger now.
Another cool thing is the power to weight ratio is approximately 350bhp/ton - it's great fun!
Sent from my iPhone using Tapatalk
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Awesome project!
Just a question about your exhaust manifold as it seems really big on the choke area... What size is it?
Just a question about your exhaust manifold as it seems really big on the choke area... What size is it?
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2,287 Posts
Brilliant result, what a great build as well!
I love the calculations on the primary alone gaining you way more power!
Good to have you back on nutz as well mate, it's been to long!
I love the calculations on the primary alone gaining you way more power!
Good to have you back on nutz as well mate, it's been to long!
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374 Posts
What a fantastic read with some proper engineering and interesting stuff. I am off to look at your build thread now. Keep up the good work.
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1,184 Posts
Thanks all for the kind comments, much appreciated 
The engine itself has done around 500 miles since the dyno session and it's been beaten on a lot!
The power is addictive, amazing response and makes for a good Sunday blast!
I'm currently reviewing my next stages with the car / engine setup but I really want delve further into the cylinder head development. I currently have a bp05 / bp4w / bp6d cylinder heads (mk1/mk2/mk2.5 heads respectively) in my garage that are ready to be stripped of cams etc.
The idea will be to use a big bandsaw, cut 2 cylinders off the casting, and 'dissect' the separated chambers to see how thick the castings are, visualise the flow paths and see which head will facilitate a big change in the port shape.
Then, I'll play around with some clay within the port to find the shape Which works best - this will be proven via a flow bench which I'm going to build this winter via David vizard's method.
What I'm hoping for is the VVT head has a thick enough casting so I can play around with port shapes, get a significant amount of flow, get a set of custom VVT cams re-ground and make a bit more power but also fatten up the bottom end with the use of VVT to control cam timing events. This is the perfect solution, if the VVT casting isn't good enough then I'll have to live without VVT and stick to the previous head castings.
I also need approximately 44mm ITB's so unless I can get my current jenveys bored out to 44mm, I'll have to sell the 42mm and get some 45mm, although 45mm are a tad big for the stock block, 7400rpm redline application.
Once I get going with it I'll take some pictures and start a new thread!
Sent from my iPhone using Tapatalk
The engine itself has done around 500 miles since the dyno session and it's been beaten on a lot!
The power is addictive, amazing response and makes for a good Sunday blast!
I'm currently reviewing my next stages with the car / engine setup but I really want delve further into the cylinder head development. I currently have a bp05 / bp4w / bp6d cylinder heads (mk1/mk2/mk2.5 heads respectively) in my garage that are ready to be stripped of cams etc.
The idea will be to use a big bandsaw, cut 2 cylinders off the casting, and 'dissect' the separated chambers to see how thick the castings are, visualise the flow paths and see which head will facilitate a big change in the port shape.
Then, I'll play around with some clay within the port to find the shape Which works best - this will be proven via a flow bench which I'm going to build this winter via David vizard's method.
What I'm hoping for is the VVT head has a thick enough casting so I can play around with port shapes, get a significant amount of flow, get a set of custom VVT cams re-ground and make a bit more power but also fatten up the bottom end with the use of VVT to control cam timing events. This is the perfect solution, if the VVT casting isn't good enough then I'll have to live without VVT and stick to the previous head castings.
I also need approximately 44mm ITB's so unless I can get my current jenveys bored out to 44mm, I'll have to sell the 42mm and get some 45mm, although 45mm are a tad big for the stock block, 7400rpm redline application.
Once I get going with it I'll take some pictures and start a new thread!
Sent from my iPhone using Tapatalk
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1,231 Posts
Can't wait to see where this goes and will be very interested to see all 3 heads cross sectioned.
There's really only one image online of NA/NB heads dissected and unfortunately they look to be out of position with each other so not of much use?
https://goo.gl/images/ayhyTk
If they are in fact inline with each other, I think you may end up with an NA head ...........
I think I had a copy of Vizards book about 25 years ago when I had my first mini and seem to remember that the inlet port should turn toward the valve before the seat? I may well be wrong so please feel free to correct me.
If you look at any honda VTEC head that's certainly what they do.
The image above shows the NB port hitting the back of the valve at quite an angle and there looks to be more meat to play with on the NA.
Super excited to see what you come up with, this is by far the most informative and pragmatic n/a build on here.
Thanks for sharing.
Sent from my Pixel using Tapatalk
There's really only one image online of NA/NB heads dissected and unfortunately they look to be out of position with each other so not of much use?
https://goo.gl/images/ayhyTk
If they are in fact inline with each other, I think you may end up with an NA head ...........
I think I had a copy of Vizards book about 25 years ago when I had my first mini and seem to remember that the inlet port should turn toward the valve before the seat? I may well be wrong so please feel free to correct me.
If you look at any honda VTEC head that's certainly what they do.
The image above shows the NB port hitting the back of the valve at quite an angle and there looks to be more meat to play with on the NA.
Super excited to see what you come up with, this is by far the most informative and pragmatic n/a build on here.
Thanks for sharing.
Sent from my Pixel using Tapatalk
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Please do this, the internet needs this information to exist, I'm so excited to see it!
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I'm pretty excited too, it'll be a fun winter project!
Sadly I don't have a spare VVT head to chop up at the moment but I do have a bp05 (93-97 mk1) and a bp4w (98-00 mk2).
I have stripped two out of the four cylinders on each head so I can get them cut from the original casting. I have various cuts I need to do so I can see casting thicknesses in different areas - should be good fun. The plan is to get these cut this weekend so I can have a good look at them over the next coming weeks before starting any actual port work which will probably be around November time looking at my current commitments/lack of garage time for October!
I think I'll start another thread similar to my previous head porting one, as this thread isn't really the place!
Sent from my iPhone using Tapatalk
Sadly I don't have a spare VVT head to chop up at the moment but I do have a bp05 (93-97 mk1) and a bp4w (98-00 mk2).
I have stripped two out of the four cylinders on each head so I can get them cut from the original casting. I have various cuts I need to do so I can see casting thicknesses in different areas - should be good fun. The plan is to get these cut this weekend so I can have a good look at them over the next coming weeks before starting any actual port work which will probably be around November time looking at my current commitments/lack of garage time for October!
I think I'll start another thread similar to my previous head porting one, as this thread isn't really the place!
Sent from my iPhone using Tapatalk
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873 Posts
I think your going about this the wrong way, cutting up the heads is not going to help at all. the reason being the inlet valve head diameter dictates the size of the throat diameter below the valve seat depending on how downdraught the ports are And the port dia which runs from inlet manifold. If they are already at optimum or bigger than optimum size then removing material is not needed.
How about measuring the throats and port Dias on the heads you have then see where material needs to be removed. Once identified then remove material. But I wouldn't destroy a head just to see how much material there is. Wouldn't it be better to size the ports and throat first Dremel where you think material needs removed. Why cut up a cylinder head if you aren't removing material that ultimately leads you breaking through into the water ways.
Just my advice opinion.
How about measuring the throats and port Dias on the heads you have then see where material needs to be removed. Once identified then remove material. But I wouldn't destroy a head just to see how much material there is. Wouldn't it be better to size the ports and throat first Dremel where you think material needs removed. Why cut up a cylinder head if you aren't removing material that ultimately leads you breaking through into the water ways.
Just my advice opinion.
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Never asked and it's been bugging me, 210hp at the crank yeh? Also more progress please
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Hi Shadow!Never asked and it's been bugging me, 210hp at the crank yeh? Also more progress please
210bhp at the flywheel, 191bhp at the wheels is what she made
Around November time I went to blyton park with the car, found the additional power much better, the chassis loved it but the rear tyres not so much! Toyo R1R tyres are really soft, after 10-12 laps they were very squirmy and the rubber was peeling! Good fun though.
Progress wise it's been pretty stale if I'm honest, The car is away for the winter ready for the next set of upgrades, of which I'm still working on most of them!
The main upgrade is I'm building a flow bench so I can create a really good cylinder head port design. I studied my power graphs and I think there is a fair bit of improvement to be made on my current cylinder head porting, but I'll be proving this on my flow bench for CFM and port velocities before installing! (I started another thread for this, which I need to update also as I've done a fair bit of work on the head already!)
The car also needs a custom air box as it breathes somewhat hot air in the engine bay, I'll design and make this all being well.
Finally I'm tempting to fit some star mag 13" wheels on the car, mainly because I have more sidewall for some 'additional suspension/forgiveness in the ride' but they also save me 0.9kg per corner of mass which is significant. Downside is they don't fit with the Wilwood 280mm Beale setup on the front so I'm looking at some custom 270mm 2 piece discs/modding the calliper mount bracket (not sure I'll get round to this though!)
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