My apologies if this has been covered before - I couldn't find anything by searching.

Everyone knows that Datrally manifolds are "better", but I'm wondering how much better they are.

The motor in my temporary rally car is a mild L18 that was originally built for twin SUs (under the old PRC rules), and is now going to get a pair of 40mm Dellortos. I figure I'm safe in assuming that there's no point in me chasing a Datrally manifold for this motor, but I can't help but wonder where the horse-power level is that makes it worth ditching the Lynx manifold.

Anyone got an idea?

FWIW, I had two "Lynx" manifolds. One definitely is a Lynx one (It has "Lynx" cast into it) the other is similar, but has more curved runners, and some other casting differences. Maybe different batches? I'm using the one with the straighter runners because the other one was ported to take 45mm carbies.

If you look at the runner size of the Datrally manifold, then the Lynx one, you'll notice that the Datrally one has MUCH larger ports.
It's desinged for use on L20b+ engines, and when used on smaller L4's (L14, L16, L18) you'd find that it'd give 'poorer' performace
due to low gas speed because of the large port size - UNLESS you have one hell of a screamer L16/L18.
So, IMHO, you'd want to use the Lynx manifold.
Remember, low to mid RPM torque & power is want you want when Circuit racing or Rallying

_________________
Classic Auto Fabrications:
http://www.ozdat.com/forum/viewtopic.php?f=38&t=31659

http://www.lescollinsracing.com/

that would explain why my old L18 was so gutless at low-rpm then.

_________________
1971 Datsun 1600 - Z18ET
1996 Suzuki RGV250 VJ22
1996 Suzuki RGV250 SP VJ23

The lynx is ok for 40s or small choked 45s ie 32mm.
Its very restricted in the center of the runners.
The flow is not that flash, but better than a single.

The Datrally/powerplay/works copys work quite well on mild 1800s.
It all depends on choke sizes & cams.

_________________
A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

Yep, Lurch has a good point about air-speed, but if the lynx manifold is going to have a big negative affect on flow when compared to the Datrally - thats not a good thing either.

The issue of poor air speed is very much just a low engine speed problem... for your rally car, there should be no real drama's. Also the fact that your running twin 40s (choke size will prob be 34-36) means that there will not be a huge low air speed issue at all through the rev range - allthough you may find an issue with flow.

I guess you have to decide if the extra flow (or lack of turbulance) gained from the datrally manifold is going to make a differance on your particular engine, with those particular carbs.

In a little while i'm going to test both a Lynx style and Datrally manifold with a set of 45's on my brothers (very mild) L18powered car - not for research purposes but because i'm gunna pinch the Datrally manifold for my car, so he will have to go to running the Lynx

FWIW, i have a set of twin 40's on a datrally style manifold on one of my L20b's and i am quite impressed with how it runs, it pulls well right through the rev range, and is quite driveable, it wasnt lacking flow either! - and although i have no facts to back up the "impressedness" or an equation to prove that i was impressed, i guess its just another thing to concider

Cheers Sean

LS,



I had the Lynx manifold on my car for the past 12 months or so with twin 40's (before recently finding a 'proper' Datrally one).
It ran at the last dyno-day with the Lynx manifold, and it got roughly 58kw at the wheels.

I then had it back at autotech just before the Natcap to get the carbs jetted properly. The preliminary run then got 59kw with the datrally manifold....and I couldnt feel any difference driveability wise.

So, long story short - No help with your original question, but yep, I reckon you'd be wasting money looking for a Datrally one for the current engine, but I would be very interested in hearing from you if you get the chance to test the standard & ported Lynx ones back to back!

On an L18 would prob be O.K - I ran one for a number of years. They actually have thick side walls so can be enlargend to fix flow issues.

Mine had been been matched (b4 I got it) to a very large port 1600 SSS head, which is prob as large as you can get an L series head (fia excluded), in actual fact the manifold was larger than the ports on the head - which was a worked A87.