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OBDI Factory vs Dinan Throttle Body Overview

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  • OBDI Factory vs Dinan Throttle Body Overview

    I decided to contribute an MForum exclusive in-depth observations of the e36 OBD-1 (m50/s50US) between the factory vs the bored out Dinan (figured it would be good information and reference since most what is out in the other forums are OBD-2 related and comparison of the Riot Racing one).

    Stock OBD-1 (Left) vs Dinan BBTB (Right)

    Here are the claimed specs of the Dinan TB per Dinan: Part: D760-0050

    Dinan's High Flow Throttle Body improves intake air flow for additional horsepower and torque gains. The internal diameter of the stock M3 throttle body has been increased for additional air flow area.. The resulting increase in air flow provides more horsepower and torque throughout the rpm range, with noticeably quicker throttle response. Features:
    • More Power (1995 E36 M3): + 8 HP @ 3500 RPM, + 12 LB-FT @ 3500 RPM (coupled w/ engine software)
    • More Power (1992 E36 325i): + 8 HP @ 6000 RPM, + 7 LB-FT @ 6000 RPM (coupled w/ engine software)
    • More Power (1993-95 E36 325i): + 7 HP @ 6000 RPM, + 10 LB-FT @ 4500 RPM (coupled w/ engine software)
    • More Power (E34 525i): + 8 HP @ 5500 RPM, + 8 LB-FT @ 5500 RPM (coupled w/ engine software)
    • Improved throttle response
    Bore Size:

    Stock: Outer diameter measured around 66mm front and back

    The inner diameter was interestingly 1mm smaller in the inside because of an internal polished raised lining that seems to reduce friction for airflow and the butterfly paint opening/closing. In other words, the airpath goes from 66mm to 65mm before out to 66mm.

    Outer/Inner diameter measured around 68MM front/back; (+2mm) straight bore through which smoothed out the casting walls all the way through . Interestingly the OBD-1 version could have potential for larger bore size because of the design does not incorporate the sealing profile gasket into it (unlike OBD-2 version).

    However, a +2mm bore was likely the best compromise because casting flaws likely show if larger. The original 1mm raised polished inner liner is not found in the Dinan version due to the bore through. There is an area where there is residual traces of the polished liner (probably due to casting flaws).

    Throttle Plate:

    : the throttle plate measured about 1.8mm in thickness and is affixed using shorter, oval head Philips screws onto the throttle arm. Also notice how the front lip of the TB where the rubber elbow connects to is a rounded/tapered edge.

    I did not measure the diameter of the plate because I didn't want to unscrew or remove it from the throttle arm but one can imagine that it is sized accordingly for smooth operations and proper vacuum. I ran a UV light through it to show the even light leakage of the throttle plate

    Dinan: the throttle plate thickness is about the same as stock at 1.8mm. However, the screws used to affixed the plate to the throttle arm is T20, flat head, and slightly longer than stock. Also notice how the front lip of the TB where the rubber elbow connects to has been machined flat.

    I also did not measure the diameter of the Dinan plate because I didn't want to remove it from the throttle arm. After running a UV light through it, the Dinan plate definitely was larger and has tighter clearance than the factory one; especially on the sides next to the throttle arm. Also felt like it caused slightly more resistance/less smooth operations when opening the throttle butterfly the first 1-2 degrees. Otherwise, it did not stick or anything.

    Final Thoughts: Based on my observations, this is probably one of the last mods you would want to do if you were to prioritize intake, exhaust, or ecu tune. Since my car is basically stock, I doubt a 1-2mm larger bore opening would have made a difference in performance.

    Dinan's claimed HP results are also questionable because it was not based on the standalone TB. Rather it is in conjunction with their Stage 1 Tune for OBD 1. I am willing to bet that the results have more to do with the Stage 1 tune which leans out the AFR by 0.5% and advance ignition timing by 1-3 degrees throughout the map than actually the results from the TB. If I look at some of their old literature, the software alone results in the same level of HP/TQ gain without the throttle body which by itself claims +9hp/13tq gain @ 3500 rpm

    Regardless, this is probably a nice to have since it is still increasing the area of the intake tract and you are installing a clean T/B with refreshed hardware. Note that I was not able to actually install the Dinan TB in my car nor will I since I sold the TB before I could. The new buyer installed it into his car and claimed there was noticeably improved throttle response and power down load. However, he also has the euro airbox, MAF, more aggressive cams, headers, cat-back, and a custom tune.
    Last edited by bmwstephen; 07-06-2022, 09:18 AM.

  • #2
    Great write up! I been wanting this but still not sure if it’s worth it.