Thanks for the replies regarding gearing. I have decided not to engage in that mod, per the replies. IAnyway, since the ecu is easy to install, and something I can do myself, for that matter. I drive mostly on the freeway, and frequently engage in WOT sprints, would the JWT ecu give me much benefit. I miss that rush to the redline, that I expierenced after about 5,000 rpm in my old 91, would I get that back, after the ecu install? It seems like that 10% loss of torque that Q45tech was refering to, makes the accelration a little "smoother", but I would like to get back that "rush" I used to have in my 91. I guess what I'm wondering is, Is the ECU worth it in the 94, will I "notice" a difference? Can anyone with a 94, comment on before/after with it? Thanks, again. I would like to do SOMETHING to my Q, aftermarket. Trying to figure out the best route to go, seems like the ecu is the best way to go, and save any other money on a new skyline

That's a VERY good question.

Off the cuff I would think them eiethr equal or give the ECU'ed one a <slight> edge, except against maybe a 90 or early 91 which I think might still be slightly faster.

All of the above would certainly be very close.

Fred...

Off the line I don't think you'd be as fast as a 90-93 because the first gear of the transmission is geared less aggressively. (I don't know the exact gear ratios, Dennis probably does).

I still think you won't get the full benefit of the ECU without the TCU. The TCU is what determines where the redline is. I think the JWT TCU will shift around 7500 rpm, whereas the stock TCU wants to shift before redline, maybe 6500-6800 rpm.

The ECU just elimates (or raises) the rev limiter. It doesn't affect the shift points.

So if the ECU is giving you more power in the upper rpm ranges (4000+ ??), you'll only get half the benefit if you keep the stock TCU.

That's just my understanding of the issue.

Greg, Thanks for bringing that up. That was the point I was trying to make, although people seem to think the TCU isn't neccasary in the 94, since it shifts in 1st gear anyway. I was thinking, it should be installed along with the ecu, to take full advantage of the setup. It seems to me, like you are selling the mod short, if you keep the stock tcu, and can't take advantage of the additional revs. You would get increased power with the ecu, but being able to rev past 7,000 would be nice. Maybe someone has a dyno sheet of a stock vs jwt, so we could tell how much hp/torque it is generating past 7k, compared with shifting up a gear. Well anyway, I'm going to get both, unfortunately I don't know anyone in AZ who sells the tcu, hopefully I can order one. I don't want my car to be dead, waiting on a core replacement. Anyone have an answer if a 94 jwt ecu is quicker then a stock 90-93?

Quicker than a 1990-1991? Probably not with the greater weight and the earlier model's lower gears. I don't think an extra 700 RPM at the top end will buy you that much.

Not to put too fine a point on it, but what real difference does it make in everyday driving? How many WOT runs do you make to the same particular higher speed do you make every day? I don't think it is a major real world concern, unless you cruise for early 1990-1993 Q45s to street race.

Lawn mower racing is a lot cheaper and won't affect your insurance and driving record as much.

Lawnmower racing, lol...

I don't really street race anymore, I was more wondering if I would get that nice rush after 5k, like in my older one. From various dynos and posting, the ECU does add around 20 hp/tq, correct? From other postings on the yahoo boards, I have heard people say after the end of first gear, the 94 will begin to pull away, which would make since, if it was pushing close to 300 hp, and 320+ ft/tq. The ECU doesn't just add revs, it adjusts fuel mapings/turns off lower octane saftey function, and other things which actually do add power, or so I've read previously. Well, I'm going to get the ecu, and see what happens. I'll report back, ont he before/after.

Based on published numbers, I'm not sure the early cars are all that much faster anyway contrary to popular belief. http://home.attbi.com/~etyppo/q45_road_tests.htm is a summary of all the Q45 tests I could find. There is variability between the results, but the results don't correlate to the year of the car. The fastest quarter mile time/trap speed is a 90, but the second slowest is as well. If you want to get technical, regressing the year of the car against 0-60 times, quarter mile e.t. and quarter mile trap speed doesn't result in statistically significant results. My 93 felt like it pulled harder at high rpms than my 95, but butt dynos are not very reliable. I'll get my 95 to the dragstrip one of these days and see how it did compared to my 93 (15.05 @ 93.x mph).

Quote » I was more wondering if I would get that nice rush [/quote]

I guess it depends what (you think?) you are on.

That's why those K&N filters feel so much faster.

The JWT ecu increases the torque by 10% by removing some of the factory safety reserve [built in to allow for abusive non maintenance owners] and bad gasoline.

So 307 vs 292 [94-95Q] is the generally accepted real torque output of the 2 versions of the same displacement engine...........15 lb/ft is insignificant in a 4300 pound car unless you consider gas mileage.

The problem is the area under the torque curve as the 90-93 tend to be much more peaky [4000-7000] whereas the 94-95 are better at low rpms and cruise thanks to the redesigned lower runners, injector type [4 holes instead of a single pintle opening], and the oval with injector notch head port allowing better fuel mixing at lower air flow speed.

The only time 750- 4000 rpm is important is zero to 30 mph [and a no down shift 25-50 mph acceleration in 2nd gear], other than that a downshift always gets you above 4,000.

Whether an extra 5-7-9-11 lb/ft is important at 2000 rpm [60 mph] depends on whether you are driving in a hilly area or a flat expressway. If the car can make the hill without downshifting the mileage will be much improved. Just like a seesaw a change at one end of the rpms causes at change at the other end.

As a lux cruiser the 94-95 engine is better, smoother, less peaky and delivers almost the same acceleration as the earlier version.

The 8% higher gearing in 1st on the 94 coupled coupled with the 15 lb/feet less peak from engine should be something like 35 effective less torque or roughly 0.3 second difference BUT we are unable to dyno the idle to 4,000 range effectively due to errors created as TC efficiency changes. So a stop watch and repeated trials are necessary and these bear out the premise.

Since the ecu change doesn't affect things below 2500 rpm WOT and doesn't reach meaningful amounts till 3500 don't expect a measureable amount below 30 mph with an ecu change.

Same with exhaust and input mods, the restrictions are all above 4,000 rpm [where they are just faintly measurable to begin with].

For monetary reasons no cams were changed [in 94] to take advantage of the redesigned heads since they knew they would have to detune the engine [by reducing cam duration, ovelap and remove the VVT in 96 to meet emissions.

In relative terms whether 1st gear x diff has a 9.1 or a 9.85 is miniscule compared to more modern 13-14:1 total gear multiplications.......8% vs 30-40%

Quote »no cams were changed [in 94] to take advantage of the redesigned heads [/quote] I wonder what different cam profiles would produce?

It's very interesting to note the better low rpm running, and maybe explains why the 1st and 2nd gears are shorter in these transmissions.

I seldom go above 4K-4.5K rpm, mostly because things go by real fast when I do, no matter the gear. I respect two tons accelerating in traffic.

Another argument for stock, unless you want to spend big bucks. Nissan engineering is quite systematic, and not just piecemeal to grab another car magazine column header.

Thanks again for information not available elsewhere!

Thanks Dennis for a GREAT post!!!

When timing mistakes happen or cam slips one tooth 10 degrees more retard yields a felt increase in extreme rpm power but a very ragged idle, the engine will run with 20 degrees but not idle below 1000 rpm.

engine simulation software indicates another 10 degrees would be optimum 258 vs 248 exhaust duration with 38 degrees vs 28 degrees of over lap but the VVT changes this this to 8 degrees above 4600 rpm.............the extra duration changes the cam peak torque up from 4,000 to around 4,500 rpm but the runner length is still tuned for 4,000 so you get less than half of what is possible.

Changing cams would be pretty useless unless you redesigned the total intake and exhaust manifolds then you could see around 360 HP at 6800 rpm but it sure wouldn't idle anywhere near smooth [lopey] at maybe 1,000 rpm which would require a redesign of torque convertor.

The fully variable VVT [2002 Q] [instead of 2 step 90-95-and 97 later] takes advantage of this [how they are able to spec 340 HP] and still meet emissions.

You just can't change 4 cams and expect much improvement!

Quote »The fully variable VVT [2002 Q] [instead of 2 step 90-95-and 97 later][/quote]

I didn't realize the cam advance was a two step operation (like VTEC, although this includes a different cam profile also) as I assumed it is continuously variable. Where's my manual, Joe?

Maybe the VK45DE (or especially the VK45DD, if we could get it) is not such a bad engine despite its less robust lower end.

I might learn to tolerate the strut front suspension without the upper links. Can't wait until the 3rd gen Qs start rolling into T-3 with the sealed transmissions.

Thank you again Dennis.

I Bet my 95 would hit 60 in first with the JWT ECU....saving the time of shifting second. Might leave the 94/95 a little ahead of the 90-93 at the end of 1st or 60mph.

1333/1.08= 1234 rpm per 10 mph= 58-59 mph at 7300 rpm less any tire/TC slip.......lets say 55 mph.

Even the 94 stock ecu allow the quarter to be completed in 2nd.

These shifting seconds add up, but still I like the thrust of 90-93 in the 55-85-90 mph range and the 98 mph second gear the 7300 rpm redline gives in passing mistakes [that extra 5-6-10 mph by chosing manual #2 before the pass].

One second at 90 mph is 132 feet!

Great posts, thanks alot. Very informative. I guess my only last question is, does anyone here have, or has driven a 94, with the ecu mod performed. I know it doesn't make much (any) difference, in the lower rpm ranges. That's fine, I'm looking for some more WOT thrust, which I hope can be gained by this mod. Can anyone with some experience of driving a 94 with JWT ECU comment on the gained performance?

Allow me to share some experience. My wife's car is 92 with JWT engine controller, and is a hairy assed ape-- torque wise and when it 'comes on cam', the rush is almost scary.

A couple of years later I picked up a near cherry 94 Q45 (both are 'active' cars btw.

The 94 was not slow, but just did not have the 'punch' of the 92.

However, I have been regularly using fuel injector cleaner (every month Techron, every 3 months STP) in the 94, and Marvel Mystery oil in the crankcase along with Valvoline semisynthetic 10w30 winter, 10w 40 summer. Now the 94 is almost as 'scary' as the 92, and the 'on cam' rush is just as strong. The significant increase in performance was surprising to me, particularly since there was absolutely no indication of any fuel injector plugging (very smooth idle), etc.

I must surmise that the intake valve tulips were badly carboned up. I have not adjusted or cleaned anything else that would account for the remarkable performance boost.

Texasoil, how much Marvel M. O. did you put in the crankcase?

I add one pint to the crankcase. That works well leave the oil level 1 pt low and top up with MMO.

"I must surmise that the intake valve tulips were badly carboned up"

Common problem with city driving [with/without the monthly blow out].....shows that even the best gasolines don't always have enough detergents.

Why I use BG44k a week prior to each oil change [every 90 days] and the rail flush at least annually along with a intake fog clean and a manual TB clean.............overkill maybe but it works.

And after using BG products [exclusively] for the past 7 years [175,000 miles+ what ever the dealer used in first 70k probably BG as I remember] we can safely say they don't destroy injectors or other components.

http://www.babcox.com/editorial/us/us12 ... nject1.htm

Thx Texasoil!