Speedworks

Hy there,


I'm following this forum for about a month now, since I boughed my 94' FD. and already I got a first clue how and what.

My engine (as well as the car) is 100% stock, putting up the 240 original european HP's (I hope i t still does)

Engine history:
-Car has it's second engine since the previous owner's girlfriend (he was also the first owner) drove the car with a broken waterpump. The car ended up at the Belgian's Mazda importer getting a complete new engine incl stock turbo's.(prove on paper)
this happened at appr. 28000 miles.

Current status:
-body: little under 66000 miles
-engine: little under 38000 miles.

I guess the engine is still trustworthy as the owner was no dumbass driver. he really knew a lot about the car, kept it running after the testdrive for cooling the turbo's and keep the oil circulating after driving (important to me as turbo driver). He had tears in his eyes when i pulled away (pretty sad)

Now, the first thing that came up to me when buying the car and modding it was the instalation o a bigger IC, preferably a front mount. Why? well first of all performance. secondly, optical improvement.
A new catback, and whenn possible a complete exhaust system would be the first things to do.

However.... i found the link to Rob Robinnet's page an started reading. especially the "reliability mods" section was interesting. So I came back from the Ic story and I'm choosing for reliability first.

So what's next?
-First I will take it to a garage of who I know they build race RX7's. A t least they will know something about it.
I will have them do the oilchange, new oilfilter, belt check.
-I will do a fuel filter change and coolant systemdrain myself.No need to pay for that and pay lots of money.
-replacing tranny and diff fluids myself or in garage as far as possible.

I was also reading the vacuum hose story, so I'm really thinking of doing that also (the intake wil have to come off so I"ll be polishing that also in the meantime)

Anyway,the vacuum job is a bit crucial so I ant to do it right the first time.
I don't know how familiar you all are with Samco hosing
( http://www.samcosport.com/ )
because i'm in touch with a dealer who can get it by the feet. ormally it's quite expensive but I would be able to get a good deal. Anyone try this stuff on his FD? quality remarks? any thing?

In the meantime I"ll be looking for an a pillar, dual gauge mount to check boost behaviour and a air/fuel meter.

Considering the exhaust mod (cat back or possibly DP,MP,catback) and intake mod I read that this can cause detonation?? Not being a big engine kinda mind Iw ould appreciate somenone explaning me what "detonation" exactly is, what the causes are, and most important, how to prevent it, as rotaries not seem to dig that.

That's about it for now I guess

any answer would greatly appreciated. And I WILL use the search option.

Neal

cpa7man

iTrader: (2)

Great post. All good thoughts and questions.
I don't have much time so I'll give you my readers digest version.
Gauges, yes you need boost and an upgraded water temp.
Down pipe, put one on asap. Assuming you have a precat. You will lower underhood temps by almost 100F. (I don't remember what Chris at RP told me, maybe 200F)
Anything more than one of the upgrades below:
catback
MP
high-flow cat
intake,
you will need a boost controller or a stock ecu upgrade. I tend to like the 3 mod rule. Although not perfect it seems safe to me.

I think the cat-back makes the most sense as the next mod. IMHO. A nice Racing Beat dual tip.

Good luck.

Almost forgot, reliability mods. Most important is the AST, the vacume hose job is not needed if boost system is working properly. Hoses are probably cooked by now and it may be an issue soon. The stock radiator is fine unless you will do a lot of track days.

You might search for "detonation". Short answer, it's when the fuel ignites without spark. Also called pre-ignition. In a piston engine the pistons rattle in the block making the rattle you hear. In a rotory the rotors have no where to go so the apex seals are stressed and usualy fail under the condition. I have never heard detonation in rotory.

racer1

DP,MP,Cat back and intake will not cause detonation, they will increase the intake-exhaust flow and that will cause you the boost to spike at the transition OR in some cases boost creep. Since you will have an increase in boost(spikes) and a stock ECU(stock fuel) that will cause detonation and your apex seals will brake.

If you are not going to change the ECU then at least install a boost controller. If you still have spikes then you'll need the aftermarket ECU. For now stick with the 3 mod rule and you'll be fine.

Instead of an air/fuel gauge whic is very inaccurate i would suggest that you install a water temp gauge since the stock one is useless.

Shad Laws

Hello-

No, that's not true... pre-ignition is not the same as detonation. They are entirely different phenomena.

Pre-ignition is like dieseling... ignition without spark.

Detonation is, in layman's terms, a "bad burn." It can happen even with a spark. In general, there are two different classes of combustion: deflagration and detonation. Deflagration is pretty gentle - it's what we try to use to propel engines. Detonation is very violent. The pressure waves travel at super-sonic speeds. For an example, compare lighting gasoline in open air with a match vs. lighting a grenade... the first is a deflagration combustion and the second is a detonation combustion.

No, that's not true...

You are correct that DP/MP/Catback/intake/etc. increase the intake-exhaust flow. And, you are correct that this can lead to boost control problems.

However, your implication that it is the increase in manifold pressure from boost spikes that is the sole cause of detonation is false.

The number one cause of detonation is that pressure is built up too high in the combustion chamber before ignition. Now, the volume in that chamber is fixed - it isn't moving :-). The AMOUNT of gas in the chamber is what we're looking for. Boost levels do effect that amount... AND less-restrictive intake-exhaust flows effect it. So, BOTH things can cause detonation.

Of course, in moderation, you can be okay. But, for example, if you take a system with stock restriction and determine that (with proper tuning) you can kick boost up to 14psi before seeing the onset of detonation, that does NOT mean that you can magically remove some restrictions and keep the same boost. In fact, most likely, you will have to DECREASE the boost.

Those of you that are quite familiar with the details of combustion dynamics will realize that I've greatly simplified and watered down the theories... but, hey, I'm trying to explain something in a couple paragraphs that most textbooks take much longer to do... so, if you realize that in the details I've made an omission in this discussion, well, tough :-).

Take care,
Shad

cpa7man

iTrader: (2)

Wow, Yes your obviously right. I was using pre-ignition to explain the idea of the fuel burning before its time. Thus causing havoc with the engine. You my friend were most probably studing thermodynamics in college while I was studying accounting.

Very nice.

Speedworks

Just thinking along... detonation will occur because of other mixture in the combustion chamber, together with higher temps in your system? Causing the mixture to pre-ignite? As I know the theory of combustion is gas,air and presure (presure, less important to gasoline engines then diesels, but ok).

I can imagine, if I'm thinking right, lowering he intake temps will retard the time of possible detonation? This can be done to either changing the intakes or mounting a bigger IC, no? On the other side, the bigger IC will cause the air to be colder, which will result in bigger expansion of the air in your combustion chamber (more pressure) which can lead, then again, to detonation.

Am I following right?

Considering the answers below and my possible plans (keep driving seq turbo's, no single unless my seq's would blow and the single is cheaper or not that more expensve then seq's)

I'm looking for about 300 HP by the end of next year, but as reliable as possible. Viewing the 99 spec RX7's from Japan (280HP) I think that's must be possible to achieve. We have small roads and trakc s are not that much around and rarely available to non-racers.

So I will only use the car during the weekend for cruises,and now and then a small race. No wrecking or breaking. The car has cost me enough and money ain't growing on my back.

Thanks for the answers...

Neal

Speedworks

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