Ok, I've found a little more info on the net:

http://forum.miata.net/vb/archive/index.php/t-18329.html

As most know, I installed an exhaust cam as an intake cam because it has more lift and duration than the intake. I had incorrectly installed my cam gear, pretty much making my last dyno tuning session a waste of time. My previous best before the Exhintake cam was 117whp and 113lb-ft of torque. That's now up to 125whp and 116lb-ft of torque. It takes the cam gears to make it work, but it's a great mod, and got me much more power than anyone would think. Here's a link to the chart.

http://www.clubprotege.com/forum/showthrea...4301#post134301

I'm using UR Ultra TRs. Cam timing is hard to pinpoint, since the exhaust cam isn't exactly 180? as compared to the intake cam. I have it set at 3 teeth advanced, then retarded 8 crank(4 cam) degrees. It's hard to say how much power was gained from cam timing optimization, and how much was gained from the cam itself. I believe most is from the cam, as I have more torque right down to 3000RPM. I'm thinking the profile of the exhaust cam is perfectly suited for the combination.

Ya, this is a BP-ZE, 1.8 with the distributor attached to the exhaust cam. There is no CAS. I had to cut the end off the exhaust cam before installing it in the intake side. I guess if your intake cam has the CAS sensor, then this mod is useless to you. Too bad though, it's worked out better than I could have hoped for.

Basically, the non-Miata HLA cams had a milder intake cam whereas the '94-'97 Miata had the same int/exh profile. Note, this changed for the NB engines and was different again for the B6. In the case of the NB, the exhaust has more lift but less duration (potentially good as a turbo intake cam as it'll reduce overlap but maintain flow). In the case of the B6, the intake cam normally provides the CAS drive, so using an exhaust cam on the intake would lack the needed drive "tooth".

Some interesting reading there.

 

It all sounds interesting, just wondering if there is a guide anywhere?
I can't seem to find one!

 

Perhaps if we can get a picture of the cams involved a solution will suggest itself?

I get the feeling that it wasn't that complicated a mod to do from the way the guy describes it and when people have done it on other cars (google exhintake) it seems you just need to make a fairly neat job of cutting the end off the exhaust cam, fit it 180* on the pulley to where it would normally be, advance it 3 teeth on the pulley and then retard it using the vernier adjustment on the pulley.

I still have no idea whether it's viable on a Mk2 1.8iS in terms of them having milder intake cams and/or the CAS being on the intake or exhaust cam though - can anyone shed any light?

 

If you don't have an adjustable cam pulley just re-drill the OEM cam sprocket at 197.5deg (IIRC).

AFAIK the mod works on the BP-4W engine but not on the BP-Z3 (because of the VVT). You still need to cut off the CAS attachment as despite there not being a cam angle sensor on the car the fitting is still on the cam, (which makes retrofitting a CAS rather easy).

 

Yes, check wikipedia for engine designations

BP-ZE - MK1
BP-4W - Mk2
BP-Z3 - MK2.5

You can't use MK1 cams* in a MK2 or vis-versa. One has solid tappets the other has HLA's (Hydrolic Lash Adjusters).

*well you can but you'd need to swop out to HLA's and lower the redline.

 

Again, great information. Thanks.

So am I right in taking from that the BP-4W has solid lifters? That's interesting as I've seen race modified cars swap their HLAs for solid lifters for more reliability at high rpm.

 

So, has anyone actually done this in the UK?

It'd be interesting to hear their thoughts on it, as well as any hints or tips.

 

I seem to recall reading somewhere that the 1999 1.8iS models have a different cam arrangement to the pre-1998 Mk 2s with regards to something like the CAS - is this correct?

Having just bought a 1999 10th Anniversary Edition, I'm going to be miffed if I can't do the exhintake mod for what looks to be a very cheap power hike.

By the way, if you check out the integral cams website linked above, their stage 1 intake cam looks to have an almost identical profile to the standard exhaust cam.

 

MK2's don't use a CAS, they have a seperate crank sensor and a cam sensor on the front of the camcover, so you should be fine.

MK2.5's can't do the exhintake mod as the cam mounted sensor moved to the back of the camcover, but the VVT gubbins also 'scuppers' the mod

 

Thanks again Mr Slow.

I'm tempted to go with one of the vernier pulleys that are on ebay for ?50 to gain some flexibility on dialing the cam in, e.g. if it's a bit lumpy on idle or not running quite right and it also means the hole will be in the right position to rotate the cam properly, even if it's a few teeth and degrees out from optimal timing.

Have you ever tried this mod?

It seems reasonably straight forward and I may well give it a go over the next few weeks, but I was hoping someone else may have tried it to give me some pointers rather than me having to do it unguided.

 

Sorry to move off topic a bit.

But above are the stock cam profiles for all but the mk2 1.6 98-01 engine.

does anyone know what they are, or are they the same as the mk2 1.8 98-01 engine?

cheers

 

There's a detailed write up of how to do the exhintake mod linked below, but be aware that the template's 197.5* positioning of the cam on the wheel may not be ideal for every engine, especially the Mk 2. It would be best to use an adjustable cam gear and adjust the cam positioning for the best power on a dyno.

http://www.diymiata.com/exhintake.html

 

There's a detailed write up of how to do the exhintake mod linked below,
http://www.diymiata.com/exhintake.html

this link doesn't work anyone know where i can find it?

 

I don't think you can use an adjustable on the BP4W as the Cam Angle is denoted by a magnetic pickup and differently cast cam wheel. When I had to stick a (kindly donated) mk1 head into my mk2, I had to change the cam pulleys and rocker cover so that it was compatible with the Engine Management. You'd have to drill it to spin it round to the 197.5deg mark.

Also, for the B6 owners out there, could a 1.8 ex cam not work on a 1.6 intake? Would it not slot the CAS perfectly? Wouldn't need to cut it then!

 

You can get adjustable cam gears with the pegs for the magnetic pick up.

 

The 1.6 I'd a shorter block, so you can't swap cams from a 1.8.

 

.

 

will do this if it works keep me up to date please.

 

Just a quick update - I've just found out that the 1999-2000 UK 10 AE and Icon versions have the more aggressive BP5A inlet cam as standard, this is a very similar profile to the BP4W exhaust cam, so there's no benefit in doing the exhintake mod on either of those cars.

BP5A cam profile

.349 lift
251 degrees duration

BP4W cam profile

.350 lift
251 degrees duration

My UKDM 10 AE's cams:

 

I have just done this on my Mk1 and its well worth it, cheap power and takes about 2 hours. Any questions, just ask.

 

I wish I understood any of this

 

Hi Will.

Heres the correct link

http://diymiata.net/exhintake.html

 

cheers Fenix!

 

Is this worth doing in conjunction with an F.I'd setup? Just thinking that the airflow is kinda already there. Any thoughts? Or experiences?

 

In principle, the higher the lift and the longer duration, the more charge you can get into the cylinder. However, if the overhap between the camshart is increased then you'll just end up pushing air out of the exhaust valve.

Without checking the profiles, I would imagine that as the standard cam profiles tend to be quite mild, a little extra duration and lift will help an FI car just as much as they would an NA car.

 

Check out the figures for all the cams on this list. Its got the standard profiles....lift/duration for N/A and F/I.

http://www.integralcams.com/miata.htm

THE f/i cams have more lift. HTH

 

If you check the Mazdaspeed stock cams to the stage 2 integral cams, the stage 2 cams have both more lift and duration:

1.8 Mechanical Lifter Cam Profiles for Turbocharged 1999-2001 Engines

Profile__________________Seat Duration__.050" Duration___Cam Lift

Mazdaspeed stock turbo___247°/251°______207.3° / 210.7°__.345"/.350" (8.76 mm/8.89 mm)
Stage 2 turbo____________257°/256°______217.3° / 218.7°__.370"/.353" (9.40 mm/8.97 mm)

For what it's worth, the aftermarket cams in my FI 2.0L Evo have a seat duration of 268° and a peak lift of 10.8mm on both the intake and exhaust, but then that has a much larger turbo to spool.

 

By the way, if anyone wants to try the exhintake mod on a Mk 2, I have all the parts you need and I'd be willing to sell them on at reasonable money. I was going to do it to my car until I found out that the 10 AE comes with the uprated inlet cam as standard!

 

Sorry to bump this old thread but this sounds quite interesting to me. Pretty sure I understand the process. Just wondering if any ECU work is needed?

The parts you need are simply an exhaust cam and cam wheel? The wheel is then redrilled and the cam rotated? Or am I missing something else?

Thanks in advance

 

Correct but all you need is the exhaust cam. No need to re drill the pulley . You just make a new mark on the pulley a certain number of teeth from the origional mark ,forget how many but will find it. Its a great mod that works.

here ya go, i tried the drilled gear but replaced with the counting teeth method and the cam timing is perfect.(its an american post)

alright, it's done, and the results are glorious. again, probably accentuated because of the itbs, but anyway, here's how you do it. unfortunately I don't have any pictures of this part because I was too busy busting my knuckles, but its pretty straightforward. Keep in mind, I kinda did this a dirty way, and only because I'm gonna replace my timing belt pretty soon anyway.

step1: remove valve cover and front cover
step2: pull the timing belt off of the cam gears with your fingers. it's doable.
step3: remove intake cam, which involves unbolting all of the cam caps. Even after unbolting the cam caps its still pretty stuck in there. I found the easiest thing to do is to rotate the cam with a ratchet, the valve springs push against it and undo the lock that the cam caps have formed. after that I was able to just pull it out. make sure you pull straight though, you don't want to mess up the cam journals.
step 4: put the exhaust cam into the intake side. Now, here's where someone who wasn't a dirty asshole would probably use assembly lube, but instead I just covered the exhaust cam in motor oil and rubbed it into the journals and lobes. I did that because my head and the cam are already broken in. It runs fine. Anyway, put it in and tighten down the cam caps with a torque wrench.
step 5: install a new cam seal on the new intake cam, then install the stock intake cam gear. the key on the cam should go into the I marked slot on the cam gear.
step 6: timing. set the exhaust cam up like normal when doing a timing belt, set the I to the I notch on the engine block. The intake cam, however, count 25 teeth counterclockwise from the E notch, and mark that tooth. Line that tooth up with the E notch on the intake side.

step 7: put the timing belt back on. here's the fun part. I'm not even going to go into detail on the quick and dirty way I put the timing belt back on, but it involves just setting the crank to tdc, aligning the gears, and man handling it back on. That said, if you're the kind of person that believes you shouldn't re-use a timing belt once it's been de-tensioned, I recommend doing this mod while you do a timing belt swap.

it took me two tries to get the timing set right with this method, but once I did it started right up.

effects: first thing i noticed, my exhaust is more burbly, which sounds sexy. it seems to rev a little more smoothly. on high rev decel it pops fire more often. as for the power, it really hits around 3600 and as far as I can tell stays until the redline. the itbs sound a little different on WOT, they shound meaner and sharper, I'm guessing because of the added duration. The extra meety midrange really kicks ass for highway driving when you part throttle from 60-70, it does it much faster.

As for overall added whp, the butt dyno says 15hp. I'm thinking my stock exhaust system is very restrictive to the itb power, and even more to the extra cam, so I'm expecting another 15-20hp from a full exhaust. i've heard itb's respond very well to more intake cammage, so you can expect more like 8-12hp if you already have an exhaust. People on mnet got 125 wheel with a stock car with a catback and this mod.

 

Correct but all you need is the exhaust cam. No need to re drill the pulley . You just make a new mark on the pulley a certain number of teeth from the origional mark ,forget how many but will find it. Its a great mod that works.

It's far better to re-drill at 197.5deg than to use the teeth, that's far too coarse an adjustment.

To be honest the best way is with an adjustable camgear.

 

i did re drill and the cam timing was retarded 2 degrees. Did as that post suggested and it was perfect at 050" lift . But i agree, adjustable pulleys are the way to go but not many people can dial them in correctly. You will get benifits by just using the origional pulley alone.Redrilling is of no benefit.

 

How has MPG been effected Slipperywhenwet?

Just to clarify, i'd need any Exhaust cam from ANY(?) mk1 1.8? (obv mine is a 1.8 NA aswell)