Trav’s Race Build: from B6 to Big Bore BP-Z3

[bartmanftw]

Not sure if I missed it somewhere but what wiring harness is in the car?
If it's still the original na6 (modified for vvt engine) there's a sensor ground wire from the ecu to the back of the intake manifold that will cause a ground loop and sensor noise if left connected with aftermarket ECUs.
Do any of your other sensors have noise in the signal, like battery voltage, coolant and air temperature?

[Scoota]

Hi Bartmanftw.

Thanks for jumping on with the advice. Very helpful.

I built the new loom "over the top" of the existing NA6 loom. A lot of the pins stayed in the ECU plugs, but a lot got pulled, and I also added quite a few new ones. I know about the NA6 grounding issue that you mentioned. I definitely pulled that one, and I was very careful to keep my body grounds and my sensor grounds separate. I'm not an electrical engineer, but I did my best. Adaptronic have a great video about "grounding discipline" and he actually refers to that fault with the original Mazda wiring in the video, so I made sure I went looking for it and fixed it up. I must have missed something though, because I have this noise issue. Adaptronic have given me some tips on how to test for ground loops, but that's not a job for today. I'm still on a high from my awesome day at Phillip Island.

I haven't checked all of the sensors, but it seems like a problem that's effecting almost everything. Have a look at the screenshot below:

Throttle Position Sensor (0-5v signal, pale blue): Very spiky. I didn't touch the throttle during this test.
Sensor Supply Voltage (~5v, white): A bit lumpy.
System Voltage (~14v, light green): A bit lumpy.
Inlet VVT1 Position (degrees of advance, dark green): Very spiky.
NOTE: I was driving the VVT control solenoid manually with a variable 12v power supply with the car idling.
RPM (lime green): One almighty spike at the 30 second mark, which doesn't correspond with a TPS spike. What the...?

Comments or suggestions?

Cheers,
Trav.

Data Log Screenshot - VVT Colenoid dríven Manually.jpg

[bartmanftw]

Hard to see the graph with the resolution.

The NA6 ground loop issue required a black/green wire to be cut in the enging bay behind the intake manifold. It was joined with a regular ground wire at the terminal so if you didn't cut it, it will still be connected to power ground regardless of what you do at the ECU connector end. If you did that then I think next step would be to conduct those ground loop tests to make sure there aren't any other points causing the issue.

[Scoota]

Hi Bartman.

My loom is extensively modified, so I'm pretty sure that terminal is no longer connected. All of my sensor grounds make their way to the appropriate pins on the ECU, and all of the "body grounds" make their way to a bolt on the back of the valve cover, which is my "one earth to rule them all".

I'll do some ground loop testing at some stage this week.

Meanwhile, I'm waiting for the camshaft advice to come flooding in.

[GR124]

Hi Trav, I have been following your build with interest. FYI i have a set of Maruha 272 cams I was going to remove from a head. They are in a BP4W head I bought from the USA. They will not suit my new build. I have not run the cams or the head as yet. PM me if you want to talk.

[Scoota]

Thanks for getting in touch GR124. PM sent!

[PaulF]

Do BP4W cams work in a BPZ3 head? I thought they were different.

[The American]

Do BP4W cams work in a BPZ3 head? I thought they were different.

Yes I don’t believe the VVT Intake cam Is compatible with others.

[plohl]

Weren't you getting cams from Comp systems? What happened to them?
BTW - cool pics

I'll close out this post with a question that has been haunting me for the past 3 months or so.... What sort of camshafts should I install into this engine?! I've looked at lots of different profiles and chatted with a few people to get their perspectives. Here are some dot points to guide your feedback:

* I don't want a "peaky" race engine that needs to be above 6000rpm to be making power.
* I want to stick to a 7500rpm rev limit, and I'd like to be shifting by 7200rpm.
* The head has been worked to flooooooow. I have installed 1mm over-sized valves on the intake and exhaust, and the head has been ported by a pro. In other words, it's ready for "bigger" cams to really get it breathing.
* I want this build to last, hence the low-ish rev limit. I know that more revs = more flow = more horsepower, but I'd rather have an engine that lasts.

What do you recommend? If you've got "big cams" please tell me your story.

• Most of the 2f BP race engines aren’t like that. I would say, the fast NA mx5s aren’t reving that high. Madjak and magpie’s builds stand out as high rev builds, but I say they’re outliners in the racing scene.
• Yep, good idea. Power from 4k to 7k will give you great go out of corners. I only rev mine over 7.5 for some specific corners.
• Do you have flow data from the head guy? Shouldn’t he be telling you what to do cam wise? Let’s be serious, if the heads been made to flow for valve lift above 9mm, and you’ve lost flow below that, you may as well start again.
• The mx5 has lots of issues when you start reving it consistently to 8k, there’s a reason why billet oil pump gears are a thing, or external pressure relief valves. You can make a very fast mx5 without reving it to 8k for every shift…

I can’t remember, but does it have shim under bucket lifters, or the standard shim on bucket? What are your plans regarding value springs? Are you happy to get rid of the vvt?

The shim on buckets are known to spit shims out at high revs – I know you’re not aiming for high revs, but everyone fucks up a sh*t sometimes. Secondly, the cams ramp is dependent on the acceleration it can achieve, which is dependant on the diameter of the buckets. The sim on buckets have a smaller diameter than the HLAs or Shim on bucket, so it’ll need a different profile… anyway, long story short, you want shim under bucket.
Once cams get to a certain size, you need to mechanically limit the VVT. The vvt control system isn’t that good mechanically, so it doesn’t matter how good your electronic control of the system is, you’re not going to be able to stop it from overshooting if you’re getting on/off the throttle quickly around the track. The risk is mashing sh*t together and wrecking the engine.

I know Gary Stewart (he’s built a lot of race engines) built a vvt engine where he mechanically limited the VVT to only have ~25* of adjustment, instead of the 40*. The most lift and duration you can have with the 40* (or 45*?) of the standard system is the standard cams. Another difficulty is you can’t easily adjust the base cam timing.

The biggest benefits of the VVT system is being able increase engine efficiency between ~2000 and 4000RPM. How often are you below 4000RPM at the track? The VVT engine powered mx5s I race against have ditched the VVT completely.

I can go into more detail, but this post is long enough.

Oh, what are you doing re compression?

Forgot you have itbs - you'll probably have a faster car without them (standard intake) and those gross air filters.

[GR124]

+1 for what plohl said.
the delete of VVT is common in race engines, the K Honda boys delete it as well. The rev range will be somewhere between 5000-7500.

[greenMachine]

+1 for what plohl said.
... The rev range will be somewhere between 5000-7500.

Thirding.

My Gary Stewart racecar engine was built to run 8k, but I ran it to 7.5 redline on the shift lights, with a limiter set to 8 for the odd corner where a saved shift mattered. The cams in that engine were optimised for power under the curve, with good punch at each change.

On cams, billets are the way to go. Welded/re-ground are cheaper, until you have to replace them, as I have done twice.

[Tim_cyc03]

+4 for what Plohl said.

I don't really know much about VVT, but if you have the ability to look at data from your ECU, check out if you actually go under the RPM where it changes? Like mentioned above, you might find you don't actually need it at all. Many things are nice to have, but it might not actually be doing anything for your lap times... if that's what you care about?

I think I have billet cams that are made locally in Brisbane, and I have a feeling they are designed by the same person who designed your exhaust. Shane would be able to confirm or deny this claim. And I'm sure we could assist if that is the way you go.

On a ported standard intake the cams were lumpy like a 13b bridgeport at idle, but on ITB's they idle nice and smooth. (not really important)

Rev range, I'm sure it has much more to do with the complete package than just cams, but I make peak power at 6,800 and shift at around 7 - 7,200 depending on corner or if trying to overtake a Porsche/Ginetta.

But again, I would have thought that your engine builder would have told you what cams to get, or spec'd the head for a certain specific cam in mind?

[Scoota]

Hi Folks.

I'm beginning to think that I may never get this thread up to date with all of the developments of the past six months, so I'll start by bringing you up to date in the present....I got the VVT working!!!! I'm a tad embarrassed to say that it was all my fault. The VVT solenoid was fine, the VVT control valve was fine, even the Adaptronic and my wiring job was all fine. It all came down to an incorrect selection being made in the ECU software. I had chosen the wrong output signal in the drop-down menu. Gah!!!! There were a few VVT-related options to choose from, and I had chosen poorly. "Inlet VVT1 Duty" was the right output signal. It seems obvious now, doesn't it? If I had known then what i know now...

This mighty revelation occurred right before a COVID-Safe sprint meeting at Phillip Island with the legends from the Alfa Romeo Owners Club Aust (AROCA), and the MX-5 Club Vic crew. The sprint meeting was on Sunday, and I had gotten the VVT working on Friday. It rained a bit in the morning, and it rained a bit in the afternoon, but the track dried out in the middle of the day and I got three (?) sessions on a dry track. Well, I have to say, the difference in mid-corner grunt was very surprising. It was obviously pulling harder, presumably thanks to the VVT because nothing much else had changed. It was a cold day, which is usually conducive to fast lap times, but I'm giving some credit to the VVT for my new personal best...

I did a 1:57.5!!

That's a full 2.3 seconds faster than my previous best in January. The cold weather and the operational VVT are the biggest factors, I reckon. I had dialled in less oversteer compared to the January setup (damper clickers only - long story, for another day), so that's another relevant factor. Still.... 2.3 seconds faster!! Its nice to finally realise some of the potential of this new engine. It was an absolute hoot!! And now, photos....

2020-06-07 Phillip Island 01.jpg

2020-06-07 Phillip Island 02.jpg

2020-06-07 Phillip Island 03.jpg

2020-06-07 Phillip Island 04.jpg

Thanks for all of the great responses about camshafts and VVT and stuff. I will now attempt to reply, starting with Shane's comments/questions...

Weren't you getting cams from Comp systems? What happened to them?
Camshafts were ordered through Competition Systems in Carrum Downs, Vic. They took my money, refused to answer my phone calls, and even hung up on me three times. The camshafts never arrived, and it seemed like Competition Systems had no intention to ever deliver them, so I eventually got a refund after threatening legal action via a carefully worded letter (my buddy is a lawyer). It was a nightmare. By that stage I was out of time to order new "hot" cams due to my Bathurst deadline. Hence, my Bathurst build went ahead using the standard BP-Z3 camshafts.

Do you have flow data from the head guy? Shouldn’t he be telling you what to do cam wise? Let’s be serious, if the heads been made to flow for valve lift above 9mm, and you’ve lost flow below that, you may as well start again.
I have no flow data. The guy that did my head had never done a BP before, but he came highly recommended by my engine builder. Therefore I don't believe he can offer useful advice about camshaft selection. My engine builder has given me some advice, which is to aim for a duration of around 270 degrees and around 10mm lift, but until he took on mine he had never built a BP before either, so it's generic advice without experience to back it up. I've looked at maybe getting the head flow tested on a bench, but it's expensive and I don't think I want to. I've spent waaaaaaaay too much on this engine already. I'll choose a cam spec and just go for it. If I go backwards and end up with a horrible engine or less power, then I'll consider getting it tested on a flow bench to figure out what the hell to do next.

I can’t remember, but does it have shim under bucket lifters, or the standard shim on bucket? What are your plans regarding value springs? Are you happy to get rid of the vvt?
I have already installed new "shim-under-bucket" valve-train hardware, all in preparation for the cams that never arrived. The specs are as follows:
* CAT CAMS TS100 Lash Caps,
* CAT CAMS CC017 Cam Followers,
* CAT CAMS S90015 Valve Springs,
* The cams that never arrived were CAT CAMS 3702606: 278/278 durations with 9.95mm lift, VVT active.

Regarding VVT... Yeah, I'm pretty keen to keep it at this stage.

Once cams get to a certain size, you need to mechanically limit the VVT. The most lift and duration you can have with the 40* (or 45*?) of the standard system is the standard cams. Another difficulty is you can’t easily adjust the base cam timing.
These are some very interesting comments, and I appear to have some conflicting information at this point. My engine builder measured the clearance from piston to valve and I am told that we have around 5mm to play with on the standard camshafts (utilising the full VVT travel range). If what you are saying is correct, then he must have got it wrong. Either way, I will be measuring this clearance again before making a final decision about VVT. A while back I stared at the internals of the VVT actuator for a good hour and I couldn't come up with a way of mechanically limiting the VVT travel that I was happy with. If anyone out there has details of how Gary Stewart did it, I would be keen to chat.

Oh, what are you doing re compression?
I've installed the 11:1 Supertech pistons and a Flyin Miata Cometic 0.040" head gasket. The aim was always 11:1 on 98 RON Premium juice. My engine builder has told me that my compression ratio is around 11:1, but I haven't seen it measured/calculated. I'm keen to measure/calculate it. Forgive me folks, I've been busy.

Forgot you have itbs - you'll probably have a faster car without them (standard intake) and those gross air filters.
Yeah, there's a lot of work to do on the air intake front. I'm not happy with the current setup for a bunch of reasons. I've come too far with the ITB's to just ditch it all, so I will work on improving it. My plan is to fabricate a plenum to go over the trumpets and bolt up to the ITB's. The filter will go upstream in a box which is pressurised by a duct/scoop at speed. It's been done on BMWs quite a bit, but I've never seen one on a BP. Something like this...

BMW ITBs 3.jpg

Tim_cyc03, thanks for your comments.
I don't have data-logging while I'm on-track, so I don't know when I'm shifting, but my limiter is currently set to 7,200rpm and I generally don't hit it (the power is tapering off a tad before that). I'm very interested to hear more about the cams from Custom Exhaust Systems in Brisbane. They were an absolute joy to deal with, so I'll be giving them a call.

GreenMachine, I totally agree... Billets are the way to go.

Some other comments...
* My engine is 1930cc - just keep that in mind.
* Does anyone know the magical Gary Stewart BP camshaft specs?
* What cam specs would you suggest for this engine?
* I still have electrical noise. I haven't tested for ground loops yet.
* If someone can recommend someone to flow test my head, I may consider it. Anyone?

I've been going around in circles a bit with regard to camshaft choices, but my current preference is to order the CAT CAMS 3702606 camshafts. These cams will allow me to keep the VVT in operation, but still give me plenty of lift and duration to unlock the horsepower that lurks within my heavily modified head. Hopefully it won't be too "peaky". Here's the datasheet...

http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=351&CAMSETUP_id=2335

Regarding VVT... Yep, I want to keep it operational despite the overwhelming majority suggesting that I should ditch it. I expect I may have to limit the travel to prevent expensive internal collisions, and I may eventually get to a point where I realise that the base timing would be better off somewhere else. But until I learn those lessons the hard way I will continue to plan around keeping the VVT. It certainly adds an extra layer to the challenge, and I'm up for that! Thanks everyone for chipping in your 2-cents worth (or your $200 worth Shane!), and please keep the comments and advice coming, even though it seems like maybe I'm not doing as you suggest. If the VVT proves to be folly, I will have proven you all right!

[bruce]

Look up Magpie's build - he's gone through all the different iterations of box design for his ITBs.

[Tim_cyc03]

CES didn't do my cams, Gary did, and he also spec'd those headers.

There is a whole area on these forums covering ITB's, and in that there is a topic called ITB Plenum/Filtration/Airbox. I'm not sure if you have seen that since you are saying that you haven't seen any BP's with plenums as mentioned?

viewtopic.php?f=88&t=66397&start=60

How many HP's/torque are you expecting from this engine?