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 Honda DOHC D16a9 twin cam engine swap/conversion FAQ 
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 Post subject: Honda DOHC D16a9 twin cam engine swap/conversion FAQ
PostPosted: Sun Jan 29, 2006 9:38 pm 
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Can i fit the DOHC engine out of a CRX or a Rover Gti into my Rover currently fitted with a SOHC D16a6?

Yes you can.

Where can i get them

From the Rover family the early Gti's had them, they ran a cat and this engine was the D16a9, the later Gtis and 216 cabriolets with catalytic convertors and lambda sensors ran this engine with a slight revision dropping the compression ratio to 9.3:1 and was labeled the d16a8.

Then from the Honda side a Concerto or CRX is the place to go, again the engines are the same codes generally however there is a d16z1 which comes from an automatic concerto i believe.

Do i need to make or buy any custom parts?

All the engine mounts and drivetrain is identical to swap over. Just a few ancilleries to change.

The dissy i have has 5 wires on the main plug not 7 like the SOHC dissy. Do i need to swap the whole loom over?

You can swap the loom but using the original engine wiring harness is fine, you just need to alter the dissy plug from the 7 pin round SOHC one to the DOHC 5 pin and run the other 2 wires to the cam sensor on the exhaust cam. All the pins are the same colour between the SOHC and DOHC counterparts so its no real headache, you just need a nice thin screwdriver to release the pins from the multiplug

Ok, that sounds straight forward enough, what else will i need?

DOHC ECU - although it will run ok with SOHC for a while, can always chip a SOHC to run DOHC anyway
DOHC dissy
DOHC upper rad hose - £38 fom Rover
Small hydraulic hose extention with M18x15 female and male end to extend your SOHC PAS hose to reach the DOHC pump, (this is easy than swapping the hfullose, and there no risk of breaking the steering rack housing)

What gearbox can i use?

Any from a Rover will do as the all have the same mounts and also the same driveshafts, there totally interchangable. The SOHC gearbox is more of a crusier unlike the close ratio DOHC gearbox from the 'sportier' models, SOHC 4th gear is about the same as the DOHC 5th and with the DOCH doing 4k at 70mph it can get noisy.

so is there is an advantage to crx ecu

CRX's don't have lambda sensors so not ideal for cruising economy although the ignition map is a little more aggressive.

I'm aware the ECU i have was pre cat, just wondered what the Idle Mixture Adjustor was for as its not directly connected to the ECU.

This adjustor is known as the CO pot in the Honda manuals, and the PGMfi system shows errors with this as a code 11. Its used to adjust the CO level at idle etc to ensure the emissions are clean. This is mainly useful for MOT time if your CO levels are too high, but thats about all, a lambda sensor is far better.

It does indeed trace back through the wiring loom to the ECU though.

Can i turbo it?

Yep, with some research into a turbo install you can quickly figure out what you need to add and whether you wish to go this route for more power. Just bear in mind Honda Turbos tend to prefer an owner who can keep a good eye on things

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This particular example is a DOHC engine using a std Rover T25 turbo. Operates with 5psi and makes 185bhp and 155lbft used as a daily driver.

Engine swap sounds alot of work, Can I not just VTEC it?

Unlike the SOHC block which can take the D16z6 and d16y8 heads the DOHC has a different head bolting pattern so nothing is interchangable with the other D16's. These D16 VTEC lumps produce around 125bhp and are the SOHC VTEC heads that operate VTEC just on the inlet valves.


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PostPosted: Sun Jan 29, 2006 11:49 pm 
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excellent FAQ guide Jonny, should eliminate some of the same questions popping up now D16 powered cars are becoming popular to use as a base for modifications. Nice to see my engine bay looking nice and clean, my 'kit' could now do with a bit of a clean :)

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PostPosted: Mon Jan 30, 2006 12:00 am 
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Nice one mate, answered everything i can think of there!

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PostPosted: Mon Jan 30, 2006 12:27 am 
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Nice one...

Should also point that the SOHC D16A6 is the same as the D16Z2, so the above applies to Z2 engined cars too.

Also the DOHC is called the ZC in the states.

Just thought I'd mention as that always brings up confusion.

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PostPosted: Mon Jan 30, 2006 3:23 am 
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Can't I VTEC my non-VTEC DOHC with the head from a VTEC DOHC?

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PostPosted: Mon Jan 30, 2006 10:52 am 
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Ruairi214 wrote:
Can't I VTEC my non-VTEC DOHC with the head from a VTEC DOHC?


different series of engine compared to the sohc vtec which makes it nigh on impossible. (yes, it can be done on F and H series for the smart ones).

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PostPosted: Mon Jan 30, 2006 10:52 am 
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nope

edit: you beat me to it lav :P

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PostPosted: Mon Jan 30, 2006 12:04 pm 
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The ZC is actually a D16a1 and uses a different cam cover and one gearbox bolt hole is different. Its the same engine as in the 84-87 CRX mk1 with the brown cam cover.

The ZC cams, intake and exhaust fit the D16a8 and D16a9 models though as the internal parts didnt change.

The SOHC A6 lumps (some yanks call this the ZC SOHC was also numbered the D16z2, these were for the automatic cars with Honda liking number specific engine applications but seems they found there way into the Coupes. Probably when Honda stopped using the engine they simply sold whatever was left/they could to Rover.


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PostPosted: Mon Jan 30, 2006 4:57 pm 
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sticky?

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PostPosted: Mon Jan 30, 2006 5:57 pm 
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ross_lewis wrote:
sticky?


Will be going to the FAQ once people have had chance to ask questions.


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PostPosted: Mon Jan 30, 2006 6:28 pm 
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Brilliant FAQ! Shame you didn't write this a month ago when i was doing my A8 conversion lol! :D

How much roughly, do you think it would cost to turbo and get it running well?

I'd put a cheeky comment about your ecu's in there aswell jonny! :wink:

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PostPosted: Mon Jan 30, 2006 11:37 pm 
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just a footer to it- how often is can i put a b16 in, asked?! possibly worth having that as a Q, and an answer o yes but its this this and this. Saves of the same question over and over again.
ah who am i kidding :roll:

:EDIT: Oh, and possibly worth saying somthing allong the lines of it being highly plausable to make B16 power, on a D16a9 with simple/moderate modifications; ie no turbo.

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 Post subject: Re: Honda DOHC D16a9 twin cam engine swap/conversion FAQ
PostPosted: Tue Jan 31, 2006 1:14 am 
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Jonny 5 wrote:
[b]Where can i get them

From the Rover family the early Gti's had them, they ran a cat and this engine was the D16a9, the later Gtis and 216 cabriolets with catalytic convertors and lambda sensors ran this engine with a slight revision dropping the compression ratio to 9.3:1 and was labeled the d16a8.


Ive bought a D16a9...(Still to fit it!)

Will the current manifold line straight up with my standard cat?

Will I have problems with the fact I've no Lambda sensor hole on my downpipe? Can I do without? I'm keeping my standard Ecu (sohc) for the min and selling the dohc one to free up a little cash. I do plan to ask if you'll sort out a remap on my Ecu which we've chatted over p.m's before.


Thanks Lee :)

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 Post subject: Re: Honda DOHC D16a9 twin cam engine swap/conversion FAQ
PostPosted: Tue Jan 31, 2006 4:11 am 
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Lee wrote:
Jonny 5 wrote:
[b]Where can i get them

From the Rover family the early Gti's had them, they ran a cat and this engine was the D16a9, the later Gtis and 216 cabriolets with catalytic convertors and lambda sensors ran this engine with a slight revision dropping the compression ratio to 9.3:1 and was labeled the d16a8.


Ive bought a D16a9...(Still to fit it!)

Will the current manifold line straight up with my standard cat?

Will I have problems with the fact I've no Lambda sensor hole on my downpipe? Can I do without? I'm keeping my standard Ecu (sohc) for the min and selling the dohc one to free up a little cash. I do plan to ask if you'll sort out a remap on my Ecu which we've chatted over p.m's before.


Thanks Lee :)


The thing is for simplicity right now (IMHO), I'd keep the DOHC ECU I gave you and use it with said manifold and engine - they're a proven matched set with no lambda to worry abou.

You'll need money later on for a Jonny5 ECU if that's the longer term plan, and I'd sell the DOHC ECU then if needs be, or get that remapped.

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PostPosted: Tue Jan 31, 2006 12:23 pm 
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DOHC ECU you have for the engine and manifold combo need the CO pot installing in the car aswell, and then probaly adjusted to suit.

Easier to get an M18x1.5 Steel boss and take it to any garage to get welded in near the downpipe to cat flange. Then its ready for future work.

The SOHC and DOHC maps have identical fuelling, just the DOHC has more ignition advance. So if you run the SOHC with a little more base timing at the dissy there should be no immediate need to upgrade the ECU. Save that for when you mods are on and you want a full Rolling road tune.

FYI: The DOHC base ignition is 16 degrees BTDC whereas the SOHC is 18 degrees.

DOHC with some head work and a skim to raise compression, decent breathing mods and maybe some Crespo cams could make around 165-170bhp like a B16. My stock D16 and B16 lumps were pretty damn similar power/torque curves, just the B16 didnt die off like the D16 so the torque fell away around 1300rpm later = much more power. Its still a pretty sweet engine and nice and light.


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PostPosted: Tue Jan 31, 2006 9:38 pm 
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Firstly whats a CO pot? :?


So you'd recommend me getting that steel boss welded in and connect up the lambda sensor?

Would be ok for the time being to run with the Sohc ecu with the lambda sensor wired in? All Ive got left todo is get a 2" centre section and new rear box and then I will be ready for the remap (Already got the de-cat/induction)

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PostPosted: Tue Jan 31, 2006 10:01 pm 
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Just to add Im getting one welded in! My g/f's dad can do it (Bargin lol)

Would one off a Sohc be alright to use lambda sensor that is?

Thanks :)

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PostPosted: Wed Feb 01, 2006 11:37 am 
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All lambda sensors are the same, and the Hondas on OBD0 all use the single wire type, so using your lambda would be fine. Will need to lengthen the wire maybe, or release it from the main loom and drop it down behind the gearbox into the section of downpipe that all the cylinders go to.

The CO pot is the adjustor next to the ECU on the 216 non cat models. This is why you cant really swap a non cat ECU into the car and expect it to run perfectly well. Theres no idle mixture adjustment (IMA) to adjust the Carbon Monoxide levels at idle (hence CO pot) so you will get the code 11.


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PostPosted: Wed Feb 01, 2006 6:35 pm 
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Ideal Cheers for that mate this topic has been a great help! :D

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