Which is the best system for a 12a and why, DLIDFIS or MSD? What is the best way to optimize them on a stockport with the usual carb/header mods?

 

What does "best" mean? DLDFIS is cheaper. MSDs improve low-RPM driveability drastically due to the multiple sparks. DLDFIS also does not help with a rev limiter, while for an extra 20% on the price of an MSD 6A, you can get the 6AL instead which does have a limiter. (And a leading-only limiter works great on a stock port engine)

Interestingly, I don't think either system has been repeatably proven to make any HP gains. But the first time you drive the car after installing an MSD direct fire, you will be amazed at how easily the car starts under any conditions, how smoothly it runs, how much better your fuel economy is.

Note: I'll spend $250US for an MSD setup that has dubious power gains, but I'm too cheap to spend $300 or whatever it is for a Yaw carb. Call me eccentric

 

peejay,
I spent money on the Yaw carb and I am amazed at the difference in power, well worth the money spent. My next step is MSD, the basic 6A is only $135 from summit or jegs. Do you think the limiter is worth the extra?
hanman

 

By the way, check out the thread on mazspeed about the MSD vs DLIFDIS.
GEO46, a racer with a good reputation did a dyno test on both of them and the MSD came out the winner easily.
hanman

 

Really? I've been looking for that thread and couldn't find it. (BTW I'm SPRT on Mazspeed)

I think the limiter is worth the extra $30. It comes with 3k, 6k, 7k, and 8k chips - probably the 8k is ideal and is what I'll be putting in the '85 (yes, I've decided to put the MSD in it). With a totally stock engine it will not go over the rev limiter unless you plug in the 3k (it'll shoot right through that on trailing only). I remember one day when my car was running very poorly, felt like fouled plugs, I just sat at the side of the road and FLOORED it - the engine just hung right there at 7k, which is the particular chip I had installed. (Turned out the problem was the accelerator squirter block had fallen out and was resting on top of the venturis! It was hosing all sorts of gasoline into the engine)

Obviously though it will work past even an 8400 pill with a modded engine If you want to cut it that close, I'd recommend also getting a standalone limiter for the trailing ignition (either a soft-touch or an RPM-activated switch that cuts power to the trailing coil) or simply not relying on the rev limiter, and just use it only as a safeguard against missed shifts.

But oh yes, if I could do it all over again I'd get a 6AL again! I figure it's only 30 bucks extra, whereas to get one separately is $50-80, and you don't HAVE to use the limiter - you can just leave the chip out, or plug in an absurdly high one that you'll never ever rev up to.

 

GEO never messed with his timing or carb mixture screws. I noticed a difference on mine when I changed my timing.

 

sprt
thats funny. different alias for every website just like me.
btw im mel at mazspeed

 

duh, I guess I am stupid. I am hanman on both!
Now everyone is going to know who I am! What am I going to do?
Now everyone will find out about my sickness..........rxitis.
hanman
dave

 

Dyno Dave here. Did I miss something with Geo's tests? Last quote I heard from him was for the runs I did with direct fire and modified plugs. Both of those had a msd for leading, ignitor running thru distributor rotor for trailing. Still haven't tried dlfswhatever on dyno yet.

 

I'm etherhuffer here as I am tired of getting asked why I use dumptruck! We're on ya now hanman!

 

And here we are again...I'm glad jeff20B piped in quickly this time before the dyno test became undisputed evidence. The guy that ran that test offered to run it again and optimize each combination to see which would come out on top. No one stepped forward to pay his bill, so it'll probably never happen. As he put it before, the DLIDFIS is a cheaper route to direct fire that is as virtually as effective as the MSD route. Jeff20B stated in the Mazspeed site (for those that can't find it...) that he dropped 4 degrees of timing on his 12A after he got his setup working and developed more power. This was never done on the dyno and the tester said it might skew his results.

Again, peejay displays his brilliance! I was wondering how to rev-limit the trailing side w/o buying 2 MSD's and never thought of the rev-window box even though that's slated for the nitrous. Now, I've gotta get another one. That is true "out-of-the-box" thinking! Thank you, sir!

 

Ok, I went and found Geo's stuff. Too bad I missed it, would have loved to harass him about being down on horsepower. BTW, just to fuel the fire: Don't assume that the timing will recover the lost 17 ft lbs. The evidence is that dual ignitors don't work. The theory is that there may be a reason they are not working. Sorry Jeff, gotta side with Stuka on this one. For today...

Just to help validate Geo's method, 2hp is about what I got going from msd with cap and rotor to msd with direct fire and side fire plugs. 2 different cars, 8 months apart, same results.

 

I was never expecting DLIDFIS to beat the MSD but it's definately an improvement over stock. I recently put mine back on and the car pulls noticeably harder and the plugs stay cleaner. In my mind the little improvement the MSD may give is not justifiable for the expense. For me anyway.

 

One timing setting that worked well with the stock setup and DLIDFIS didn't work very well with the MSD, and vice versa.

Hey REVHED, are you still getting misfires?

 

Misfires? The only time I ever had misfires was when I tried your first suggestion of hooking up two coils in series running off the one ignitor.

 

so should I get an MDS or try to hook up the DLF(insert alphabet soup here)?

Mike

 

It depends on how much cash you have.

 

MSD.... Probably the best money I've ever spent on my 7.
In my opinion, the $130 -150 is justifed compared to the price of most mod's on these cars. It seems as though the MSD has had different and varying results for those who have tried it - why not try them both and return either the second ignitor or the MSD depending upon the results in your particular case - either set up is an easy install and you won't be waisting too much of your time - my 2 cents...

 

I'm betting Jeff's sitting on a few thousand ignitors. Soon as everyone on the internet starts buying up ignitors to use on their Honda's and such, supply and demand kicks in and Jeff moves to Redmond to hang with Bill.

Someone went and rated this thread, so all you escapees are outed for eternity, if not longer....

 

I wish I had thousands of ignitors.

 

I was thinking of going the DLfisdiswhateverthefuck, but my local parts store wants $209.00 for a new ignitor. Im hitting up the boneyard later and gonna see if I can pocket a few. Ill let you all know If I get any.
I hate to jump on someone else's thread with my own related questions so Im off to start my own thread....

Mike

 

Thanks for all the information and advice. I will sit down today and write a summary of the numerous posts. If anyone has anything else to add, please can they do so in the next 24 hours so an overview can be posted tonight.

It is now five o'clock Monday morning, its raining and I have a seven hour drive in front of me to get to work. This gives me plenty of time to think of whether to install DLIDFIS or MSD. I converted the posts to audio CD which will be played as light entertainment on the way.

 

You sound like me Paul, scrutinize everything from every possible angle bfore attempting something. Of course this is the best way, so I think. Less trouble in the long run. Might wanna download some music from http://www.winmx.com and add a little music on there ... LOL

 

DLIDFIS or MSD…… an informed overview

WHY CHANGE FROM STOCK

The stock RX-7 ignition system used on Gen 1s from 1980 is perfectly adequate for average use. Gen 1 carburettor cars benefit more than EFI cars from ignition modification. A more advanced system is apparently better for high performance/race situations.

Both DLIDFIS and MSD are improvements that should give you the benefits of direct fire, but no one has yet used dyno testing to quantify the benefits. These potential benefits claimed are:-.
· better low rpm quality feels better particularly where street or bridge porting has been undertaken;
· starting is easier especially in cold weather;
· power may be marginally up, indications max 2bhp but unproven;
· cleaner emissions;
· fuel consumption may increase by 2-3 mpg; and
· cleaner plugs


INSTALLATION

How to install both systems are well described on links from the forum
DLIDFIS at www.geocities.com/cd23c By Jeff 20B
MSD at www.mazspeed.com/msd by Mikey D
For general comment read the forum threads under search ‘DLIDFS’ or ‘MSD’ As usual Paul Yaw has something to say, look under ignition. MSD has its own website.

For stock ports just MSD on the leading ignition is satisfactory. It is sound sense if you go to the limit to buy the AL6 to get a rpm limiter as it is not much more expensive than the A6, about another $ 30. If you are racing it is best to add a rpm limiter to the trailing ignition or use two MSDs. Using Peejay’s system, as described on this thread, for rpm limits is useful on the DIDFIS system

The critical point is that the optimal timing is different for stock and both modified systems. For DLIDFIS drop about 4 degrees of timing, try for 10 degree leading/trailing split for a 13b and 8 for a 12a, but not less than 20 degrees for leading. If you don’t tune you can end up in a worse situation than stock. Some of the apparent improvements come about by tuning alone not just adding the system.

For both systems to work well think about upgrading the plug wires to say 10 gauge.

If you have an early 12a replace the points/external igniter with an aftermarket electronic ignition.


WHICH DIRECT FIRE STSTEM- DLIFIS OR MSD?

DLIDFIS can give you most of the advantages of MSD.

The basic cost of MSD is about $150 plus coil, but more as you add to it for serious racing situations. DLIDFIS is cheaper especially when you already have some of the spare parts. Using old parts to build a DIDFIS system can be a mistake if the parts are substandard. Second hand coils can be suspect so why waste the system, High performance parts are not necessary, as stock parts will give adequate performance, unless there is genuine need for a hotter spark when a MSD Blaster coil be useful at peak revs.


CONCLUSION

My conclusion is that if you want to get the fill benefits of any significant performance improvements, say above 140bhp, go for a direct fire system. The modification will be a relatively economical way of having power once basic mods such as a header have been done. On balance, a carb upgrade comes first before an ignition upgrade, as marginally does a fuel pump upgrade.

If you want the best then think about MSD, but DLIDFIS will give you almost as good results at a lower cost especially if you already have the parts. Both systems are relatively cheap and if well set up can do no harm. But you must get the new timing right or you are worse off apart from looking cool.

I am going for DIFDIS using Jeff20s article and Revheds layout


Have I made any mistakes?

 

1) We're not looking for theories, we're looking for solid facts that are fair to both sides, ie. optimized timing and jetting for both systems on the same engine on the same dyno on the same day with the same gas.
2) Backing off timing on a 455 Pontiac to 36 degrees BTC all in at 3000 RPM from 38 degrees BTC will net 30 HP and as much torque, so timing changes backward can be a significant factor. Whether jeff20B is calling from the seat of his pants or had a G-Tech to read off of, he still said he gained more acceleration IHOP from decreasing his timing settings. He had said this on his first round of articles after renaming his idea from "PMDFILS" or whatever BEFORE the dyno tests. Until someone steps up to the dyno again, we'll simply never know. The one true fact is, you're still running three coils, two firing directly into the plugs. With side-cut plugs, that's gotta be worth more than 2 HP...
3) It's 6A and 6AL (as in Limiter) on the MSD boxes, Paul. Nice summation. It should be stuck in the archives, so the next round of tifoso can simply be directed to it instead of rehashing this over and over and over.....