aronmatic

Hello Guys
Is there anybody, who upgraded the turbos on c63s, without upgrade the downpipe and cats. I dont want to change the sound of oem performance exhaust system. Its perfect for me. No problem, if i lose some ponies.
Any experience?

tobeit

Not sure why you are asking but as far as I can tell all turbo upgrades don't require (its entirely optional) DP changes...more important to change intake when adding bigger turbo's.

aronmatic

I dont want more sound and dont like the smell from catless/race cated downpipe.
Hard to go back to stock.
This is the main reason.

tobeit

same here... then don’t. Not a requirement when upgrading turbos. You could even opt for the Weistec stage 1 upgrade...they upgrade your OEM turbo and after it’s installed nobody could tell visually it’s different.

LessIsMore

Without upgrading the exhaust or intake, upgraded turbos will be choked significantly. You will need to run lower boost than you would if you had those mods. You will also probably experience increased lag because an upgraded Turbo will have larger heavier wheels that take more time to spin up, and you do not have the offsetting benefit of having opened the intake and exhaust post turbo, to help spool time. And lastly the aftermarket turbos, which in all cases are less reliable than OEM turbos, is going to be under more stress because It won't be able to get air in-and-out as easily as it needs to for its flow requirements. Usually upgraded turbos without the supporting mods will leave you disappointed. I definitely think you will see a increase in power, but you will always be significantly lower than those who have the right supporting mods for a proper set up.

tobeit

intakes absolutely as I said earlier but DP’s don’t think so. Look at Renntech and Weistec and they produce their largest turbo upgrades w/o DP changes. Yes, it sure will help but none include changing the DP as it’s technically not legal. They produce north of 800crank w/o it.

JPM-3

Do Pure Turbos stage 1 and intakes seem good for around 590 to 600 whp? I'm thinking to just skip the ECU tune only and just go upgraded turbos from stock without going too crazy.

AlexZTuned

The stock cats flow more than enough for upgraded turbos. Maybe you’ll miss out on 25 hp.

LessIsMore

What are you basing that statement and hp figure on? Even Renntech disclaims that their turbo upgrade won't hit the numbers without downpipes, bov adapter and high flow filters.

Factory downpipes don't rob a consistent, static hp figure. It's a percent of what you would have optimally made with maximally-flowing exhaust. So if you gain ~30whp with dp's on a stock motor, could probably expect a significantly higher delta on upgraded turbos than what you would make with dp's. The bottleneck effect grows as you try to cram more through.

LessIsMore

Read the fine print on Renntech's product page. I think you may need to remember that the engine, exhaust, etc, is a system.

Look I hear you man, Having no cats can be smelly and expensive. Who wouldn't want to skip the down pipes if the factory ones would do the job. Sure, you can do it - I am not even saying that upgrading turbos without down pipes is "wrong"; just certainly not optimal. And that you should be realistic about expectations in that case.

LessIsMore

Are you saying you are planning to not even get a tune for the upgraded turbos? That is crazy.

Rochviper

So many opinions its hard to vet out the facts. But what about hi-flow cats in upgraded turbo applications? I've seen some comments about they have 95% of flow of catless pipes but I find that hard to believe.

tobeit

I don't think its all that confusing. If you go bigger and dont want to change the sound of the engine as the OP wants to do, you don't need to changed DP's and can get 800-900 crank.

https://www.renntechmercedes.com/ind...205-c63-detail

https://www.weistec.com/w-4-turbo-upgrade-m177.html

Both are compatible with stock DP's...and surprisingly both only want you to change the intake filter to a high flow filter, not even an aftermarket intake.

Now, you can add aftermarket intake and DP's and gain some more, but not required to upgrade the turbo's. I think most would tell you the first you should consider is the intake as they are more restrictive than the DP's once you have bigger turbo's.

JPM-3

Clarified- meaning Pure stage 1 + intakes + tune as opposed to just a "stage 1" ECU tune. Would this be good for close to 600 at the wheels?

LessIsMore

So Renntech's dyno charts only show 610 WHP for R3 (which i think is a misrake in their site since their product page for the r2 pkg also shows 610 whp dyno) but lets say its actually 660 - which is 725 or so at the crank using modern trans loss of 10%. Far from 800-900.

No idea how Weistec is going to make 950 horsepower without larger down pipes. I just flat out do not believe that claim, TBH. I'd love to see you try though.

tobeit

I just gave round numbers for general idea and only Renntech and Weistec as examples. Renntech estimated 767crank in the table above the chart, close enough for me. Pure has tons of charts depending what else you do...and seems also in the range. In general, Renntech's packages are always most $/hp and usually also on the conservative side of what they claim.

LessIsMore

Sorry but that sounds like you're moving the goal posts.

My point in this thread is that engines are a system, FI motors are especially sensitive to intake and exhaust components having adequate flow to support power , and you cannot make the power if you can't get enough air in-and-out. If you don't have the proper supporting mods for the Turbo, you will not be able to fully realize the full power gains of the turbo. It is as simple as that .

Rochviper

I agree that you "can" leave the stock DP's and cats. When I look at Renntech site, I see they are getting 610rwhp with their turbo upgrade. I think the catch is they are using 20% loss calculations to get to their 760HP rating. Every tuner I've talked to says to expect 650rwhp to 670rwhp with turbo upgrade and catless DP's on 93 pump gas. So right there is a 40-60 rwhp gain by going with catless DP's.

tobeit

I am not moving the goal post - I answered the OP's question that you don't need (read "must do requirement") to change the DP when upgrading turbo's. I just gave a rough range you can achieve w/o changing the DP's...according to people who sell them as kits and have various options from just upgrade OEM to replacing them with larger turbo's. No need to argue.

PS: Does not mean you don't get further improvements in performance if you do change DP's but again you can get very nice power upgrades w/o it if you don't want to change the DP's.

LessIsMore

Yes, exactly.

Also - The reality is that tuners inflate advertised numbers to sell turbos and packages. And you cannot just slap big turbos on an otherwise stock car and expect to achieve those numbers, or usually even close.

LessIsMore

That seems like a reasonable expectation. Consider: people hit mid 550 whp pretty easily with just intake, tune and the right fuel.

tobeit

I think it depends on the seller/tuner....Renntech are usually more conservative and in general I would trust them with their numbers. Their numbers often look underwhelming because of it (just compare the $23k R3 package they offer against competitors). Others might be off and in fact some even state those numbers depending on x, y, z to achieve (pure gives quite a lot of charts with different bolt-ons, race gas or standard but mostly provide what configuration was use, Weistec is more elusive)

LessIsMore

Anyone using a 20% drivetrain loss on our cars is inflating numbers, and i wouldnt trust their claims unless some independently verifies it. Dont get me started on Renntech's cost:hp value, and I see nothing conservative in their claims. Turbo sellers across the board routinely tout the max-effort/full-build hp you can get with a turbo, i.e. the upper limit.

Suggest calling some of these sellers/tuners and asking directly, what whp you can expect with just their turbo and tune ... see what they say.

tobeit

I am lost what you arguing. Seems you argue to just make a point of some sort. I am out - OP got his answer that he can upgrade turbo w/o changing DP's and get pretty good gains.

PS: Doubt Renntech overstates their whp...that what matters at the end.

LessIsMore

This has been pretty civil and straightforward, sorry if it's too much and you are lost. This is a discussion not an argument. I'm just offering my knowledge and experience to help the OP make an informed decision, and contradicting some mis-information and misleading claims along the way.

PS - please try to follow, I never said whp claims are exagerrated. It is the crank hp claims that are often inflated by using drivetrain loss corrections that are too high. To cut through the BS, people should use wheel horsepower figures and compare those. Then do their own math using around 10% drive train loss as a rough guess to crank hp.