wannabuy350z

iTrader: (27)

Hello,

The reason I am starting this thread, is confirmation on Turbo sizes and capabilities with the same pressue produced.

I would like to compare 18G (greddy) vs GT25 (JWT Garrett) Turbos.

Now I know that the greddy are a bit larger turbos, but what I am really aiming for is the limits of the VQ35DE.

I have done a lot of reading lately, and some confirmed that 10.3 CR on the engine could be rounded. I have read that many did tests and their CR were 10.1:1 or even just 10:1 compression ratio.

that being said in regards to the turbos listed, if set at the same psi level and in theory all set-up correctly and both engines are healthy as can be, the Greddy turbos will produce more power.

So my question is:

if someone has GT25 turbo's can they up the their PSI safely? (more than the standard understanding of max is 9 PSI)

as long as the tune is adjusted for it.

Sorry for the long post...

dieselmcore

iTrader: (1)

off topic:

how've u been man ?

rcdash

iTrader: (18)

The difference is that increasing the boost pressure results in less gain on a GT25 than an 18G because the size difference changes efficiency. Turbo efficiency is a measure of how hot it makes the air as it compresses it. In other words the GT25 heats the air more than the 18G as you increase boost, resulting in less net mass air (and thus power) per PSI.

wannabuy350z

iTrader: (27)

been good man, work work work!


thanks for your response. yea I understand in regards 18G is more efficient at certain boost levels that are beyond the GT25 (past 14PSI)

I guess my question is, can I up my boost on the stock block? since these are such tiny turbos compared to 18G. so the PSI produced on a GT25 (compressed air) isnt as much volume as the 18G at the same PSI.

IIQuickSilverII

iTrader: (13)

stock block? DE engine?


keep it on spring pressure or what ever gives you circa 400 whp for longetivity. But yes you can raise the boost if you want. You are just playing with fire with those damm weak rods

ttg35fort

iTrader: (2)

Here is a link to a thread that might be useful for you to review:

http://g35driver.com/forums/showthread.php?t=30171

It shows comparisons of the volumetric efficiency of the TD05H-18G, the Power Enterprise 1420, and the Garrett GT28R turbo chargers.

If you have no intention (and never will) of building a stronger short block, I think you probably will be happier with smaller turbos than the 18Gs. I expect that you would get a little less turbo lag, a little more torque under 3500 rpm, and better efficiency. For instance, in the first chart shown in the link, the PE 1420 turbo charger has better volumetric efficiency at boost levels and voumetric flows you likely will be seeing with a stock block with no more than about 400 RWHP (I'm assuming a twin turbo setup).

If, however, you think that someday you may want to go to a stronger short block (e.g. if you blow up the one you have now), then you might be better off with larger turbo chargers, such as the 18Gs. That way, you have more margin to increase power later on.

I have the Greddy TD05H-18G twin turbo setup currently being installed in my car, but I had the short block built with stronger rods, ceramic coated pistons (8.8:1), and a balanced rotating assembly. I'm also installing JWT C2 cams and springs, Ferrea valves, and a Coolingmist Meth/Water injection kit. (I am shooting to exceed 600 RWHP).

Audible Mayhem

iTrader: (48)

nice chatting with you today, hope i could help you out.

let us know if you need anything.

wannabuy350z

iTrader: (27)

^thanks, you are the only ones that gave me a good answer...

rcdash

iTrader: (18)

9 psi for a stock block is just a guideline - and yes you will increase torque less per psi with the smaller turbos. Since the rod is the usual failure point, peak cylinder pressures (peak torque) is what will determine how close to the edge you currently are. By your sig, you are at 379 whp already. I think many would agree that you would be pushing the limits of the safe zone going higher. If you're prepared for a build, then pushing the limit isn't such a big deal, particularly if this car isn't your daily driver... Only you can make that decision.

wannabuy350z

iTrader: (27)

^I thought the limit of the block under a very well tune is around 430whp. and I would like to leap into the 400's with a good tune from someone local.

rcdash

iTrader: (18)

That's not a good way to look at it. There is no such thing as a "limit". There is only statistics: the risk of bending a rod over time at xxx torque levels. I guarantee you that on average, a stock DE rod will fail sooner at 430 whp than at 380. How much sooner and will you beat the average? I don't have the data to tell you that. The risk is there though and it's better to know that going in...

I am not talking about any shop in particular (the ones on this forum are all generally pretty good at what they do), but keep in mind that a shop benefits from stock blocks blowing. It's not their fault and they will have you sign a form when you drop your car off that says "no guarantees" and most shops will tell you honestly that the more you push, the greater the risk, but the higher they push the tune, the greater the chance you'll have to come back to them to build the block. I am not commenting on anyone's ethics, that's just the way it is.

Good luck.

wannabuy350z

iTrader: (27)

^even though this has gone way of-topic, I agree with you completely.

I was just trying to get more power safely.

cbr900son

iTrader: (4)

IMO play it safe unless ur prepared to build a motor. Then u can turn it up and not have to worry as much if u blow it.

wannabuy350z

iTrader: (27)

I am leaning towards an built bottom end. but, damn its sooo much cash! my power aint enough, feels super slow nowadays...

ttg35fort

iTrader: (2)

Import Parts Pro Stage 1 is pretty reasonably priced at $2600. It should be good up to about 650 RWHP.

http://www.importpartspro.com/st1blon.html

I spent the extra $250 for the Ceramic/Moly Piston Coating on the pistons and $200 for the ARP main stud kit for a total of $3,050 plus shipping. There is a $750 core charge, but you get that back when you send back your old short block.

Kyle is great to deal with.

wannabuy350z

iTrader: (27)

is the core charge included in the $2600

ttg35fort

iTrader: (2)

No, you pay $2600 + $750 + shipping

You get the $750 back when send the core back. The shipping charges from Texas to Florida were $170, which included insurance. I assume it will cost about the same to send the core back.

Call Kyle (the number is on the web site). He has been building VQ motors for over 10 years and knows his shiat.

str8dum1

iTrader: (11)

did you rebuild the shortblock yourself? or did a shop?

ttg35fort

iTrader: (2)

My short block was built by Import Parts Pro.