Eyger

If you were to do everything possible besides opening up the engine and replacing internals, what is the highest possible PSI you can run on a daily basis without breaking things? Can you get to 250hp safely in the maximum PSI range?

I'm just curious. I seem to get mixed impressions when it comes to what you can and can't run on stock internals. Additionally, what is it exactly to be worried about when turning up the boost with stock insides?

rednwhite04

iTrader: (3)

This is a question for the turbo guys but from what i've gathered 8-9 psi is good for DD reliability. Rods can/will bend with too much boost, pistons can get ruined, head gaskets can pop (which can also warp your head). there's my 2 cent, i'd listen to what them turbo'd boys have to say.....

emjay

iTrader: (2)

if ur gona boost make sure u get arp head studs cuz thats the only insurance + afr gauge wide band .. not a lil shitty light. lol. as for max psi/power .. it depends on the turbo ... if u have a t3/t4 u'll get there with 6 psi .. with a t28 9-10 psi... its really how much power ... and 250 is a lil too much IMO with stock internals and a DD unless you are on a stand alone. other then that .. 200whp is perfectly reliable especially with our plastic intake mani's

Eyger

Not sure what you mean, if you have a t/3t4 you'll get where? to 250hp with 6psi? and you'll get to 250hp with a t28 on 9 psi? Is that what you mean?

Has anyone broken their intake manifold due to too much pressure?

speedfoos

iTrader: (17)

Understand you're not a turbo guy, but most of this is wrong.

Tuning, tuning, tuning, tuning.

As long as the engine is tuned properly, you don't have to worry about any of this. Crankshafts are designed to spin when pressure is applied at the proper point in their rotation cycle (i.e. boost). As long as that pressure is applied at the moment the crankshaft is designed to expect it for that cylinder (i.e. a proper tune), it just makes the crankshaft spin faster and with greater force. This will not harm the engine in any way - AS LONG AS ALL THIS IS HAPPENING AT THE PROPER TIME IN THE ENGINE BLOCK. The key is engine management and tuning. If I went out today and cranked my boost up to 15 psi with my piggyback, there's a good chance I could send one of my nice forged Crower rods through the side of the block.

Like Emjay mentioned, if you were running k-pro on stock internals with ARP head studs, I would say stick a cam in that bitch and crank the boost to 15 psi (as long as your compression is good before the build) and have fun with it. Anything more than that and you're rolling the dice on the stock IM.

Hope this helps. $1000 spent on k-pro is a better upgrade than $1500 spent on new internals if you had to choose between the two.

speedfoos

iTrader: (17)

T3/T4 turbos are larger and typically flow more CFM than smaller T25 turbos. 8 psi on my GT30 (T3-footed turbo) will flow more air than 8 psi on Boiler's old T25 turbo. The hp numbers he put up are just examples and not realistic results.

No one has cracked a stock IM yet to my knowledge, but I can't imagine a plastic IM will hold up very long to high levels of pressure.

rednwhite04

iTrader: (3)

double post double post

rednwhite04

iTrader: (3)

lol, I was just waiting for you to step in Clint

emjay

iTrader: (2)

tune tune tune .. and thats why i said if u want 250whp, u go kpro + arp studs because the tune with kpro = way more solid then a piggyback which is only reliable for ~200whp...

Eyger.. it doesn't matter at all how many pounds ur running, its jus psi... its how much power u make ... if i can make 200 @ 6 psi and u make 200 on a smaller turbo with 10psi, then we're both running @200whp, .... who cares if im boosting 6 or u boosting 10... anyway, like Clint said, tune tune tune ... so if u do want 250 make sure u go stand alone, but if u wanted my advice, i would get kpro and tune for around ~220-230whp cuz really, do u know ur tuner will tune u 100% reliably at ~250whp? i bet u don't and thats why it could jus be a timebomb for a stock internal d17 pushing 250 without a really solid tune.

Boilermaker1

iTrader: (16)

Old??? I still have it... its quite perfect for daily driving (even though I dont daily it anymore).
You probably can get away with running 12 psi on stock rods if its tuned REALLY well. ARP studs would be a must. The one who needs to chime in is Andy, I'm sure he's tried pretty hard to blow a stock bottom end with excess pressure.

Eyger

Hm, this is all good/funny information. So lets see if I've got this straight:

-Actual PSI is not directly correlated to horsepower produced. I.E, you can run a lower PSI on a turbo that flows more to achieve (in this hypothetical situation) the same horsepower that a higher PSI on a turbo that flows less?

-Reliability is more about the tuning of the system versus the components of the engine. I.E, the inability of a lesser engine management system to correctly control what's going on inside would be a problem for the engine, before the durability of the stock internals themselves are brought to the breaking point?

As for the intake manifold, the real benefit is? The flow of it, rather then the strength?

This is a lot to wrap my head around at once.

I still don't understand how turbos are classified in terms of size and lettering and whatnot.

So here's a good one, if a larger turbo can run a lower PSI and get the same horse as a smaller turbo at a higher PSI, would it be safer for an engine with stock internals to run a larger turbo with lower PSI?

Weird, it's easy to think that a turbo is a simple thing. And really, it is, it just pushes air, but beyond that it seems more intricate then it appears.

emjay

iTrader: (2)

lol again ... its the same thing ... bigger turbo less psi or smaller turbo more psi .. u achieve the same horsepower and that determines how much power the engine can hold... not how much boost. Yes tuning is very important but i mean beyond 250whp its a time bomb on a stock end.

ofcourse the Intake mani is more for flow .. but our d17 is plastic and can crack

and when we say tuning... a standalone tunes way better then a piggy back .. but that doens't mean jus cuz u have a stand alone ur reliable at 250 .. u have to trust ur tuner and its much much more reliable to tune with a standalone then apiggyback system, thats simply it.

Once again .. its the SAME THING to get 200whp with larger or smaller turbo with different psi's ... the only difference, the larger turbo spools slower, it has more potential if u decide to build .. while a smaller turbo is perfect for our d17s ... because it spools quick and gives u great mid range power ... while a big turbo spools slower and gives u that high end power

speedfoos

iTrader: (17)

Sort of. Once the intake mani is pressurized, then that's it. It will hold the same volume no matter what you use to fill it - a big GT45, a little VW GT20, or your own lungs. There's a matter of how much air the turbo can move to maintain that pressure in relation to the engine sucking air out of it, and at what point the compressor (turbo) becomes inefficient and simply can't move any more air to keep up with the demands of the engine. Add spool times to this and you're starting to get close.

Exactly. Forged internals are there to take the additional stress of forced induction and provide insurance for the "what-ifs" that happen on a turbo'd car - a fuel injector dying causing lean condition detonation, a mis-shift and you bend valves and scar pistons, a bad tank of gas, etc...

Again sort of. The runners on the new IM are much shorter than the stocker which will mean better throttle response especially in vac driving (no boost) and during the boost transition. The air has less distance to travel to get from TB to head with Gerry's IM. If you look at the stock IM. It's actually a long runner IM that's been folded up to save space.

Some of this manufacturer specific and some of is not. A/R is one of the key components to focus on. Check this article out:

Hotrod.com Turbo Article

You want to run a turbo that is suited for your power goals. If you only want to make at most 250-275whp, then get a smaller turbo that will spool a lot faster and you will have a nice fat powerband that starts earlier in the tach. If you want to make big power, you're going to have to sacrifice a little bit of low-RPM power as the turbo will take a little (really little, it's not like you can count it in seconds) longer to spool up and make power.


Yes, and strapping one of them on a car that was never designed for it complicates things even more!

You really should go buy this book:

Corky Bell's Maximum Boost

Eyger

^seriously I do. I think that'll be a birthday present to myself.

At least I feel like I'm learning something, which is good.

I should just re name this thread to the "Eyger's crash course in turbos thread"

Here's another one, at what point is it necessary to ditch the returnless fuel system? Can you reliably achieve 200 from the stock fuel system?

speedfoos

iTrader: (17)

You can do 200whp all day long on the stock returnless system if you upgrade the fuel pump. I know Edwin ran (is still running?) the stock pump on his setup making around 170whp (sorry if I understate yours number Edwin), but it's not a gamble I'd be willing to take. I'm still running the stock returnless setup with a Walbro pump and I don't have any problems. I have all the stuff to do the return setup, but want to break the motor in first before I go changing something else.

emjay

iTrader: (2)

less questions more searching man, all this **** has been covered so many times

speedfoos

iTrader: (17)

Meh. I don't mind. Creates more content for other folks to search on.

Eyger

The search button is overrated.

Know what happens when you search using the search button, you get endless results of people asking questions and then everyone else telling them to search! Well what the hell! The answers never really get out unless you manage to be around when that one thread answers the questions you have.

Thanks for all the info dudes. I really appreciate it.

I started this thread partially to just get some threads goin, doesn't seem to be too much activity around here, so I'd thought I would contribute.

Anyways, so far I've learned a bunch and have enjoyed hearing the conversations.