34 DMTR jetting

mmudge

mmudge

True Classic
I almost have the X rolling again but I need some pointers on air and fuel jets. Does anyone have the stock jet sizes? I need a starting point so I can adjust from there. My motor is a 1500, FAZA Daytona 30/70. My compression is a tad higher than stock. The motor was just rebuilt, but that wouldn't make much difference.

Thanks
 
stock jetting for euro 34dntr is
prim idle jet 47
primary main jet 107
primary air corrector 160
secondary idle 70
secondary main 130
secondary air corrector 150

but it's pretty common practice (and the jet is even supplied in some overhaul kits) to fit a 117 main jet to the primary side

If you have a longer duration cam (and hence generally a lower manifold vacuum at idle) it's also common practice to go for a 50 idle jet in the primary

SteveC
 
Data point for a 1300 with a FAZA 35-75 Cam and an ANSA Header. Runs really, really well.

Primary Idle 50
Secondary Idle 50

Primary Main 125
Secondary Main 150

Primary Air Corrector 160
Secondary Air Corrector 240

Primary Emulsion Tube F30
Secondary Emulsion Tube F30
 
A friends restored X19 that I did the cylinder head on and sold him all the engine parts...I recently rebuilt the carb and jetted it as per my previous post. Carb is a 34datr stock euro spec with 23/26 venturis.

The cylinder head is ex regata 1500, simple port/polish. Standard sized valves (36.2/33.4), throated seats, reworked valves...flows 105CFM @ 28" and 10mm (stock is 88CFM) ... so abut a 20% improvement over stock by hand working the ports/seats/valves. The thing with this build was ALL that got changed was the head...inlet/exhaust and cam is still exactly the same as before so ALL flow improvements are from the work performed. Carb is 34DATR so stock european for this engine, cam is stock euro cam, exhaust manifold is stock, compression ratio stock 9.2:1.

watch the first short video of a walk around and start up....The car looks, sounds and GOES really well.
https://www.facebook.com/groups/Fiat500ClubThailand/permalink/1634307583273838/

SteveC
 
Last edited:
Good grief, sounds like a 1,000cc sport bike at idle. What exhaust is on that car?
 
carl said:
Good grief, sounds like a 1,000cc sport bike at idle. What exhaust is on that car?
Click to expand...

Some off the shelf ANSA tip outlet system...bit loud at idle, but not too bad when you open it up, very slight drone around 3500rpm... not my choice of exhaust but the owner likes it. Engine uses the stock euro cat iron 4/2 manifold, so this system is simply twin downpipes exiting into more or less the middle of a single large can with an outlet tip at either end

SteveC
 
fiatfactory said:
A friends restored X19 that I did the cylinder head on and sold him all the engine parts...I recently rebuilt the carb and jetted it as per my previous post. Carb is a 34datr stock euro spec with 23/26 venturis.

The cylinder head is ex regata 1500, simple port/polish. Standard sized valves (36.2/33.4), throated seats, reworked valves...flows 105CFM @ 28" and 10mm (stock is 88CFM) ... so abut a 20% improvement over stock by hand working the ports/seats/valves. The thing with this build was ALL that got changed was the head...inlet/exhaust and cam is still exactly the same as before so ALL flow improvements are from the work performed. Carb is 34DATR so stock european for this engine, cam is stock euro cam, exhaust manifold is stock, compression ratio stock 9.2:1.

watch the first short video of a walk around and start up....The car looks, sounds and GOES really well.
https://www.facebook.com/groups/Fiat500ClubThailand/permalink/1634307583273838/

SteveC
Click to expand...
Daniel Forest said:
Hi,

Don't know waht is the 34 DMTR jetting. In fact, don't know where it came from Here is a link to a jetting chart.
https://xwebforums.com/wiki/index.php/StockJettings
Click to expand...


Thanks for the chart. The Euro 1500 did the trick. I don't have the exact jets at the moment, but close. I'll order the correct ones and be set. Ulix, I saw your text on the chart. Thanks to you also.

Mudge
 
Does anyone know why the Euro 1500 jetting is smaller than all the 1300 jetting in the wiki jetting chart? Seems counter intuitive...
 
There are about a thousand variants of the 34DMTR/DMTRA/DATR/DATRA..... so you will find all manner of variations in jetting sizing depending on application.

scroll up, I listed the euro X19 1500 jetting for that variant of the 34 up in post #4, as mentioned to you, go for 117 primary main.

SteveC
 
Sorry! I see it now, Thanks Steve!
I don't see the pump jet listed anywhere though. My old 34 has a 50, the new one I just got has a 45.. I have other value jets as alternatives, what is optimal?
 
Last edited:
Both pump jets will actually deliver the same volume of fuel, just timed differently. Volume is more a function of the pump cam and the volume displaced by the diaphragm movement, rate of delivery is the pump jet...so a larger pump jet will deliver more fuel early and less later, smaller pump jet is more even thru the cycle. Remember the diaphragm is elastic, it will store the pressure energy given to the fuel and discharge it thru as long as its compressed regardless of the orifice size...it will just take longer. (pump circuit uses a different type of fluid mechanics to control delivery/flow - it's under pressure - whereas the other fuel circuits are depression drawn.)

General rule of thumb is start small with fuel sizing and work up.

SteveC
 
Last edited:
You must log in or register to reply here.
Back
Top