I will wait for Gords response ...because he bought my 850's.....but on my car I did not feel a great difference in lag between the 700 and 850bb.....running from 60 to over 130 you could really feel that the 850 pulls better and longer......IMO.....and also on a road course....if there was significant lag....it would have affected my lap times.

 

Well again from a pump gas perspective in comparison to a measly Greddy kit, it offered much more lag and no advantage up top. Now if the tuner had gone crazy on race gas vs me max'd then it would be much more interesting.

 

Berto... keep in mind that your car is a mutant

 

I think Alberto is spot on - top end power on pump gas differs little between the two. Unless you increase displacement or rev limit, I wouldn't go up from 700 to 850 bb. The power curve shifts too much to the right otherwise.

 

If you are buying the kit new absolutely go with the 700BB kit and also upgrade from the 190lph fuel pump to the 255lph I think it is about a $500 difference now and $2500 if you want to do it later because the 700bb and the 850bb kits run different passenger side manifold than the 530bb kit so you have to buy a new manifold as well as the two new turbos so it is costly.

One of my biggest regrets is getting the 530bb kit instead of the 700kit when I wanted more I had to upgrade turbos I ended up buying XKRs 850bb kit.


As far as the lag goes when I had my 3.8L I never noticed any lag at all with the 850bb kit. But now I am running the 850bb kit on my stock engine and I notice some lag.....I guess not really lag per say but it dosent seem to really come on hard till about 15psi then it comes unglued . I also make more torque than horse power I think that might be a result of the bigger turbos For your power levels you will likely be only running about 15-18psi I think the 700bb kit would satisfy the average guys needs.

 

whew... i dont need to pick another hobbie, lol.

 

fixed

only make more trq than HP if you arent flowing well past 5252 rpms (ie high backpressure with stock cams or small exhaust/cats)

 

Here is my scientific test bench....Road course (lap times) and my 700bb / 850bb vs fully built 911tt GT2.

On track...yes I use race gas.....but against GT2 I used pump so did the GT2. With the 700bb I gave up at 130mph.....he was pulling on me too hard......but with the 850bb it was the other way around.....so I don't agree that the 850bb has nothing up top.

Either way maybe the OP could get a ride in a car with either setup to see which one he likes

 

^ I think with your 850bb, you had C8 cams and were reving to 8k? In a road race with a 3.5L motor, in the 5k - 7k rpm range, I think there will be more total area under the torque curve with the 700bb. Move the shift points up to 6k-8k with some long duration cams and I think it'd be in the 850bb's favor.

I think you can build the engine to suit either... but for a street car that will see 3k - 5k more often than not, the choice I think tilts in favor of the 700bb.

Anyway, stop arguing with me - I don't want to rationalize spending any more money!

 

Don't get me wrong....I agree that the 700bb would be a better street setup or even a better all around kit.....but I just wanted the OP to be aware that the 850bb is not that bad either.....I just don't want him to make the same mistakes I have just incase he is a boost head like me...it can get expensive swapping out turbos....

Don't fight it....I am sure before it's all said and done...you will get bigger turbos

 

Here is my proof lol. Take into account my car makes nearly 200whp more now still on pump. I recall L and S telling me the 850's were gonna yank me hard up top.Both made identical peak, but the curve down low was kinda weak on the 850's for pump use IMO, Same dyno, same tuner. Not to mention you really have to row the gears to keep the 850's spooled, not powershifting.

Of course on a closed course

http://www.youtube.com/watch?v=-gafwal26KU

 

Stock engine = stock cams.

 

man, i stumbled into the wrong thread. all i want to do now is switch to a twin-turbo kit

 

I wish that was possible.. There are hardly any FI 350Z's here in the whole country and no real ones with a built motor.

Might be hard to imagine for you guys but the 350Z is an exclusive sportscar over here. We only have the Track model and the newprice was 55k (same for 370Z right now). I live in a city of 80k people and there are about 5 Z's in the whole city. It's kinda cool (:

 

Okay you guys convinced me.

If i buy the JWT kit it will be with 700BB turbo's.

Now what about other kits like Greddy, GTM and APS? Any reasons to choose one of those over the JWT kit?

 

Alberto.......I drove in Luie's car......it did not pull like mine. Well you know more than I that a TT kit on 3 different built cars can get 3 different results. I wish you had driven it.......over 80mph to 130+ I would pull on the same car that crushed my 700bb at the same speed.

Either way...I will agree that the 850bb is not a WOW difference from the 700bb.......and yes, it reacts differently on race gas. I think I made 800 whp with it......but at least it was more driver friendly than what I have nowJ

Greddy has a good track record on here....but some have said if you are going to run it on a road course it's not the best choice because it only has single cooling.....but most have said the it's an all around good setup.

GTM has many different turbo sizes....you can custom build your kit and easy to upgrade later...plus they use Garrett BB turbo.....I use this kit.

APS..... I myself have never used that kit....So someone will answer that for you. Rumor has it that they are now using cheap turbos in their kits which will not impress the owner of a built motor.

My understanding is that your car will be a street car....So you can't go wrong with either Greddy, GTM or JWT........what you now need to do is find out which company will give you the best customer service for your location.

Good luck

 

Youy know what they say....Once you go boost there's no going back!!!

 

Responded to your pm

 

 

I have had both the 700BB and the 850BB on my car as well as the APS Extreme on my other G35. The 700BB was easily the most fun for a street driven/pump gas car. With a basic built shortblock with stock heads and cams the car made 580whp on a Mustang dyno at 18psi. Now with the 850BB and all the other crap listed below the car makes slightly more peak power but less low and midrange power at the same 18psi. Awesome.....