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924 Na VS. mid 80's RX-7

 
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marky522  
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PostPosted: Mon Aug 13, 2001 3:15 am    Post subject: Reply with quote

Anyone give me any info, i've got a buddy who has a mid 80's RX-7 in really good cond. Its all stock, but a real eye catcher. Any way i have a 81 all stock 924na and i want to know which one will win and the best place to race him??? Should i race him on the h-way where its a rolling start or would i do better from a dead stop?? Thanks, it just bugs me how he is constantly saying how his car is soooooo fast...

Mark
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MAS  
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PostPosted: Mon Aug 13, 2001 3:44 am    Post subject: Reply with quote

One of the bugbears of the 924 was the new RX7 in 1979.

I own a stock 82 RX7 (as well as an 87 924S)... anyway, the first generation RX7 is quite a bit faster than the n/a 924. The 0-60 time on the early RX7s is in the mid 8 second range. The stock 924 is around 9.5 to 10.5 secs.

The performance difference between the 1st generation RX7 (with the 12a engine) and the US spec 924 is a classic example of how two cars with similar weights and horsepowers can have dramatically different performance figures.

-MAS


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MAS  
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PostPosted: Mon Aug 13, 2001 3:56 am    Post subject: Reply with quote

Just a few more little points about the RX7s...

The 12a engine was only supposed to have 101 hp (and about the same amount of torque) for a car weighing about 2,400 lbs. The second generation RX7 (86+)had the fuel injected 13B engine (initially) rated at 146 hp... for a car weighting about 2,700 lbs. Even though these newer cars had close to 50% more hp, and only a little over 350 extra pounds in weight... they were actually not much if any, faster than the earlier RX7s. In fact, as many RX7 owners today know, some of the first generation cars are slightly faster than the second generation ones.

OK... what's the point of all this? The point is that many of the first generation cars are likely producing more hp than advertized... probably around 120-125 hp (I'm not talking about the 84 or 85 138 hp GSLSE, either). The Japanese edition of the 1st generation RX7 (called the "Savanah") actually produced something like 128 hp with the identical engine to the North American model.

-MAS
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larso  
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PostPosted: Mon Aug 13, 2001 8:20 am    Post subject: Reply with quote

THe reason the rx7 is faster is because it revs higher, allowing you to change gears later if the tranny is similar.

THe 924 turbo did 0-60 in 9.3 seconds with a 6400 RPM rev limiter, and the same test was done on another 931 with a 6600RPM rev limiter and it did 0-60 in 7.7 seconds.

IMO these figures that you read in text are not a way to judge a car.
THe 931 could be considered dead slow by looking at the specs (9.3 seconds), but when you drive it it is fast.

Another example is the corvette in 1980.
The specs show it having better handling than a datsun, a 924, etc., it has better Gs, better slalom speed.

R and T did a test on 4 different cars, the vette had the best numbers on PAPER.
The vette ended up being DEAD last in the test for handling when they drove it in REAL LIFE fast driving. They said it constantly spun out and all that stuff...it does exceptionally well in a lateral accel test, but does shit when you take it on a 90 degree turn is basicaly what they went on to saying.
I may scan the article soon and post it.
It's not how many Gs you can pull in a circle, it's you the car REACTS in REAL LIFE situations. On track, doing a shicane with different angled and sized turns, is the way to test a cars handling...not what it's slalom speed through equally laid out pilons is, or its later accel...those are much to vague and misleading.
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924RACR  



Joined: 29 Jul 2001
Posts: 8114
Location: Royal Oak, MI, USA

PostPosted: Mon Aug 13, 2001 9:29 am    Post subject: Reply with quote

IMHO, the NA 924 is a match for the 1st gen RX7. I base this on my experience and the experience of others racing them on track (road racing, we turn both ways, don't just go straight)... I've been able to pull even with 1st gen RX7's with similarly stock engines... I feel that, with a well-developed suspension and engine, I will be able to hang with the legal frontrunners. Sure, they can rev, quite true - but everybody knows they're the torque-less wonders! This is why the CRX's whip them daily. The 924 has similar advantages. Furthermore, they're using an antiquated live rear axle, which is no match for a properly set up 924 rear IRS.

In case you'd care to review the video of me dusting RX7's (especially in the corners) at Mid-Ohio and Gingerman, consult:
http://vaughanscott.com/videos.htm

_________________
Vaughan Scott
Webmeister
'79 924 #77 ITB racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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AppleBit  



Joined: 16 Nov 2002
Posts: 1516
Location: Minneapolis, MN

PostPosted: Mon Aug 13, 2001 10:46 am    Post subject: Reply with quote

Scott is right. The rx7 is a match for the 924...

When my 924 was completely stock, I could beat the first gen rx7's... I was too chicken at the time to even try against anything more

If you really want to cook that rx7, you can actually do a lot of free! and low cost modifications that will insure extra speed that you will actually notice. Just visit my website...

stock for stock- they are _very_ close though!

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Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

Porsche 924 Wide Body LS1 Corvette 500 Horsepower Engine
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MAS  
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PostPosted: Mon Aug 13, 2001 3:15 pm    Post subject: Reply with quote

Sorry guys... he's going to have a shock. The stock vs stock the RX7 will beat it in a 0-60 drag by at least a full second.

I completely agree about the 924 having the better handling/rear axle etc. The handling of my 924S is light years ahead of my RX7 (also my 924S is faster than my RX7... but we're talking about the regular 924 here).

-MAS
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F924T  
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PostPosted: Mon Aug 13, 2001 3:29 pm    Post subject: Reply with quote

As a former RX7 owner...I had an 83' RX7 (12A Engine) and a 86' RX7 (13B Engine, close to 140 lb-ft & 150 HP)...This cars are actually fast and their torque numbers are high.

The RX7 with the 12A engine will definetely beat the 924 NA and it handles extremely well. The 13B equipped RX7 will give a 931 a run for its money and possibly beat it if driven well; because of the free revving engine the car is able to stay in the power band longer with no turbo lag and better torque at lower revs; if racing a 931 against a 13B RX7 race on the highway with a rolling start, to have turbo spooled and ready to kic butt.

Good Driving cars. It just does not have the character of a 924.

_________________
Francis Asencio
'80 931...Driving and restoring.
Boy, this thing handles!

[ This Message was edited by: F924T on 2001-08-13 14:37 ]
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MAS  
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PostPosted: Tue Aug 14, 2001 4:37 am    Post subject: Reply with quote

Regarding the RX7 being a "torqueless wonder". This is actually a bit of a myth, because the rotary actually has a very good (and almost flat) spread of torque compared to the average 4 cylinder engine. The rotaries initially got their "torqueless wonder" reputation from the V8 guys back in the 70s. And, of course, compared to almost any V8, a rotary has way less torque. Mind you... the V8 guys would have called most smaller engines "torqueless wonders" too... especially 4 cylinder engines. The reason that the V8 guys even were interested in talking about rotaries back then, was because the early rotary-powered Mazdas (the RX1s, 2s and 3s) packed a pretty good performance punch for such small cars. Remember, this was way before the days of the commonplace high-performance 4 cylinder cars like the Preludes and Integras.

To give you an example of my stock 82 RX7's torque... it can easily pull (without lugging the engine) from 1,000 rpm in 5th gear (which is an overdrive) all the way to the redline at 7,000 rpm.

-MAS
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