CT458 vs CT358 what would you choose?

[A80Avant]

Im about to make my final decision about buying the turbo from comp.
Now prices of these 2 models are exactly the same.Here are their differences:

CT458:

4inch inlet 2.5inch outlet
larger compr.major impeller than the 358,turbine is the same

output(according to site 75hp more than the 358)

CT358:

comp wheel: 58/74.5mm
turbine wheel: 58/74.5mm

Both : AR 0.63

im getting the turbo with Vband to downpipe and T3 to exhaust manifold to go with a T3 to K27 flange i got from 034 and the SQ exhaust manifold.

Initially i was keeping the original inlet manifold to go with the 358 but now that i have the reverse from wagner,i thought that it might be worth going for the 458 since the amount of lag difference may be compesated through that.

what do you guys think?

[Rusty]

Knowing how much you seem to want the power I'd say go for the larger of the two and if you don't like the lag then build a stroker

[DJones]

Personally i think it is all about drive-ability not figures, torque delivery is important to me.

Is there anyway you can try other similar setups prior to spending the hard earned.. Which ever way you go you will always wonder what the other one performs like...

For torque delivery i would be going for the smaller one..

[jade]

Hi

Well I am taking delivery next week of a CT 358 k26 hotside & V band exhaust

So i will have to wait & see what the performance will be, A according to Justin it should spool 200-300 rpm earlier than the gt 3071 & is capable of 550 hp ??? so i should be able to achieve 500hp without a problem, web site quotes 475hp

I will update when mark maps my car on performance

Regards Wayne

[A80Avant]

you are right about the fact that there always be a wonder... I must admit that my car now basically boosts nicelly from 4000rpm onwards and im told that these 2 turbos may do the same on my current setup. Preferably i wouldnt want to wait longer than 4000rpm to see that top boost im going to set on the map,so yes you are right about torgue and driveability.

On the other hand, having read that the magnificent wagner IM can reduce the spool up to 500rpm,i can say that it gives me a bit more room to go bigger.

Jade will be a great assett on my choice and i will be excpecting results on that soon!!!!

Im also not sure if i will be doing any light cyl.head trimming,cause i will have limited time in Greece to do all that stuff. I can always do that in the future and remap since im going to be on VEMS.

many thanks on the answers guys! keep them coming!

[macspring]

Just my tuppence,

4K boost threshold would too high for me, I 'm currently not content with a 3K boost threshold, but then I drive around the city?

I agree with DJones, drivability should come over high power figure at high revs.

It'll be like driving with an on off switch on your engine if the boost comes in at 4k.

500bhp should be enough for the road, with as early a spool up as possible, but as mentioned above, just my tuppence worth.

Looking forward to reading your feedback on your new engine spec.

Kind regards.

[Jamo]

4K boost threshold would too high for me, I 'm currently not content with a 3K boost threshold, but then I drive around the city?

I agree with DJones, drivability should come over high power figure at high revs.

It'll be like driving with an on off switch on your engine if the boost comes in at 4k.

500bhp should be enough for the road, with as early a spool up as possible, but as mentioned above, just my tuppence worth.

Looking forward to reading your feedback on your new engine spec.

Kind regards.

Misconception by a lot of people who haven't had a car that has that boost profile.

My old K26/K27 with 7A cams drove quite well around town but then flew once you hit 4k. It was a very nice drive and not on off it was progressive up to 4k then you got a nice rush.

Just because you don't have as much power below 4k doesn't make it undriveable.

[A80Avant]

jamo is 100% there,even with part throttle and a bigger turbo you get a good rush below.Lets dont forget that it is a completelly different thing having 0.5bar of 1bar of boost down low on a bigger turbo than a K24 or an RS2 turbo

[Jamo]

The boost profile that are on off are really the large turbos or ones with huge hotsides like the K27 / K29 & GT35 or badly mapped cars ( stock RS2 ) as the difference between on and off boost are that large you register the difference instantly.

[DJones]

How about 2 to 2.5 bar low down which is what i get. For me its drivability, as mentioned.

At 100mph 600bhp cars are still catching me up because mine has up and gone. Admittably they will pass me after that but for me at 100mph the point is proved.

My RS4 wants the revs to get the power and is in my view flat low down, despite the fact it is boosting. The configuration in the UR would leave the RS4 for dead...

I appreciate that the UR is lighter and more powerful but its the power delivery i am referring to. Hence the RS4 wont stay standard...

[jogi730]

4K boost threshold would too high for me, I 'm currently not content with a 3K boost threshold, but then I drive around the city?

I agree with DJones, drivability should come over high power figure at high revs.

It'll be like driving with an on off switch on your engine if the boost comes in at 4k.

500bhp should be enough for the road, with as early a spool up as possible, but as mentioned above, just my tuppence worth.

Looking forward to reading your feedback on your new engine spec.

Kind regards.

Agreed - BTDT and got the t-shirt. Hence where I am at now.
Also agree with Jamo and Darren though. Keep mentioning old set-up, but 400bhp and driveable even off boost (not that I had much of that).
So all depends what sort of driving you will be doing andf where you want your power as to which turbo you have or go for the best compromise to suit your needs.
I'm sure if you refer to old posts, Repo would have highlighted this. I'm now very much taking his advice due to the experience and knowledge base he has.
Cheers
Chris

[repo]

I am not taking part of this discussion, as I have been ignored too many times in this particular case.

I am also most certain, whatever turbo Vas decides to take, it will not satisfy him.

[A80Avant]

thanks for your 5p anyway repo.I too can think of a few reasons of your current attitude towards my choises,but hey,i dont mind! people are who they are. No fuss

[A80Avant]

@ jogi and all,

when you are driving off boost on lower revs with a smaller turbo and a bigger turbo, does that make any difference?

When im driving around with up to 0bar boost or 0.5bar boost at most, does it make any difference the size of the turbo?

Im asking this,because if you have seen from videos i have put up here, that is what i get already with the 3071R.So since repo and justin can give me a turbo that spools basically the same as 3071R and give me more than 80hp more than what i have now, why not go for it?

Also when off boost however the car goes,depends on how lightened the moving parts are,since basically it is like being a natural aspirated car.Of course other factors come into play,like compression cams etc.

My whole idea is for the turbo to be able to produce the amount of power im after with spooling before 4000rpm and with boost less than 2bar. The amount of power im after is 500hp but with a headroom as well.Justin seems to think that the 358 is capable of that. The 458 came into play as the main difference is giving even more headroom for improvement and minimal spooling differences.

By the way, repo was giving me the option of CT355 for 'easy'500 hp but possibly with 2+bar which i prefer not,and even if that is possible (which i dont doubt) it doesnt leave any room for improvement. As i explained,this will be the permanent turbo choise for me as improvements and further steps will not be taken.SO i want to have a good range power without stretching the turbo.

[repo]

Like I have said multiple times, a 355 did 530hp /630Nm at 1.9 bar. Stock AAN head with reclocked stock AAN cams.

The smaller turbo You use to get the power, the larger the powerband.

But I have said enough. My experiences have no value here, so I let other people to take charge.