Centri v. PD - Not the routine question though

[uofipilot]

Kind of a centri v. PD thread, but not the usual.

Not lazy: Read
Kinda lazy: See SUMMARY
Really lazy: See SUPER SUMMARY

I finally started work, and have a pretty good paying job. I also have a 97 cobra that isn't fast enough. I also have a whole winter coming up, so the three might mix pretty well. Below are the three options that I'm considering for a build (in order of preference).

1. Buy a wrecked 03/04 and swap everything into my 97, except the block/crank. I'd build my teksid bottom end and use everything else off the 03/04 motor, including heads/intake/sc/and accessories. With a built bottom end, I could start with an eaton, and the sky would literally be the limit. Cons: really expensive.

2. Buy an 03/04 motor and just drop it in (I know...alot more involved than that, but you get the point). Cheaper than 1, and still would have a badass car. Cons: iron block, and somewhat limited posibilities with the stock 03/04 internals. I might also be wierd, but I'm leaning away from this because I'd like to keep my block. It's like the heart of the car, so I'd like to keep at least the block.

3. Build my engine as is for a centri, and then go with a big centri. Cons: lose some low end.

SUMMARY
The car will be 99% street driven, so I'm really looking for low end power. That said, what power range would a centri have to be in to keep up with a PD car in the low range. For example, say a PD car makes a peak 430 rwhp and say 350 hp by 4000 rpm. What peak power would a centri have to make to match the pd's power at 4000 rpm?

I fashioned this beautiful graph to help illustrate my question. How far must the the centri's curve be "slid" up to match the pd's power at the green line?

Can that even be done? I realize that the more power you make with a centri, the higher it's going to be in the powerband, which means you will be robbing low end power even more. It's a vicious cycle....

SUPER SUMMARY
How fast is a 500whp centri below 4000 rpm?

And no nitrous. I'm not dominc toretto here. (Not that I have anything against nitrous...I just want power all the time).

Thanks for reading. If this car stuff doesn't work out, I might go into graphic design. I'm clearly a master already.

 

[VtekII]

from what ive read before somewhere else you can hook a waste gate up in line with a weaker spring and then run a smaller pulley on your centri to get you into the boost fast and hard.

so i guess run like a 10 or 12lb spring in the waste gate but 15 or 20 psi pulley and u should push that blower hard. im not sure how much work is involved with setting up the wastegate but i dont think all that much.

 

[uofipilot]

I think I get what you're saying, but how would a wastegate opening at 10 pounds help it get into boost faster? It seems like running a smaller pully with lighter spring in the wastegate would work opposite each other. Like it would start bleeding boost at 12 pound but still be working to spin the smaller pulley in an attempt to make 15 pounds. I might not be getting it though.

I guess another rephrase of the question could be "Once you get into a big centri like the F1, what does the lower end of the powerband look like?" Anyone have said dyno sheet?

 

[19mustang95]

what's your budget? you need a transmission, rear end, and fuel system to support all this power you want to make..

 

[uofipilot]

I know...that's why buying a wrecked 03/04 sounds pretty good. The t56 would be great. I'm going to keep the SRA either way, and a good build could be done for about a grand with an frpp diff and moser 31 splines.

As far as the budget, I don't really know. It's hard to say, because the option that I'm leaning towards (number 1) would probably cost 15k by the time its all said and done. I dont want to take shortcuts. I could probably do a killer centri build for 10k or a moderate centri build with used parts for 5k. So I dont really know about budgets, as my options are all over the place. I think I want to decide what I want to do first, and then see if it's feasible. I guess that's why I'm asking about the centri....it would be cheaper, but if it's not gonna get me where I want, I guess I gotta pay to play.

 

[95PGTTech]

Drop in the stock 03/04 motor. There is plenty enough going on with just that swap, don't over complicate it. Get it running and do some bolt ons, they are incredibly fast with just the Eaton. You can always put the stock motor on an engine stand and build it at a slower pace as money comes in. Don't start a giant project that never gets finished, small steps.

 

[jumperjack]

If your car is going to be 99% street then the PD is way more fun stop light to stop light. The Centri IMHO is better when you start talking 550+ HP. There is no sense in making more power then you can use on the street. Gearing is a way to keep the Centri in its powerband on the street also. The Eaton swap is expensive unless you can find a deal on a complete 03 engine. Just a question of money.

 

[sc98cbra]

Depending on the boost of your Centri, You will feel the power pretty quickly.

You should be idling at roughly 1200, You smack the gas to the floor, 4000rpm is coming super quick.

Trust me, I've owned both a centri car and a 04 cobra, unless you have a TS, the eaton feels like it falls on its face around 5500, compared to a centri of course.

But the torque is different.

You can slap a set of MT's on my centri car and it will feel like it's pulling just as had as my 04 did.

 

[na svt]

PD blower all the way. 2.3 whipples and smaller KBs are cheap and will make over 600rwhp and are a helluva lot more fun to drive than a centri.

I have a complete 03/04 setup...

 

[My94GT]

hounestly when i went to build my car i wanted to do the 03 swap. at the time they were real expensive and i couldnt find one so i went with my combo i have now. hounestly if i were to re do it now id do the 03 swap even if i had to wait a little to find a motor and all. its just a great set up for a street car, makes good power and is super reliable.

 

[Tabres]

PD blower. I rode in a mid 10 second 2.3 whipple car the other week and it was unreal.

I'd swap in a complete 03/04 drivetrain if I were you and then find a used twin screw and throw it on.

 

[Cookieman00x]

My thoughts... buy an 03/04 swap already done and save a ton of money and work.

 

[97desertCobra]

My thoughts... buy an 03/04 swap already done and save a ton of money and work.

This.^^^^^

But out of your options I vote complete 03 engine swap. The 03-04 engines can handle well over 600 rwhp and be reliable. The factory eaton can take you to 500rwhp with a good port job. A used whipple 2.3 or KB 2.2 can easily make 600rwhp. But like stated anything above 550 rwhp I would consider a centri. Mostly due to traction. Having 650 rwhp in a twin screw car is cool but dancing all over the street because your tires are screaming for mercy at you isnt so cool.

 

[TIMMONS]

\ It's hard to say, because the option that I'm leaning towards (number 1) would probably cost 15k by the time its all said and done. I dont want to take shortcuts.

instead of spending 15k plus all the work and time, just buy an 03-04 :-D

 

[97desertCobra]

instead of spending 15k plus all the work and time, just buy an 03-04 :-d

+100000

 

[uofipilot]

Nah, that's missing the point. If I was just gonna buy an 03/04 I would have already done that. This cobra was the first car I bought, and I want to keep it for as long as its financially feasible. And seeing as how I paid cash for it, and it's worth 7k on a good day, I dont see me selling it any time soon.

I want to go through a build. It will probably suck at times, but it will be worth it in the end.

 

[venom1997]

get a 2.1l kb with water meth and spin it to 12-14 psi easy 420-450 hp add a small 50 shot of n20 and 500+ kb are perfect for street

 

[uofipilot]

Venom, I love your kb car. I want to go for something like that, but I figure I might as well go to c heads and an intercooler while i'm doing everything. This thread makes me lean further towards my first two choices.

Thanks for everyone's input.

 

[mpe331lx]

Can that even be done? I realize that the more power you make with a centri, the higher it's going to be in the powerband, which means you will be robbing low end power even more. It's a vicious cycle....

That is an inaccurate statement. It is true that a centri blower makes most of its power up top, and produces more power the faster you spin it (until you max out the blowers efficiency range). BUT there is no trade off in power like you are thinking. You are confusing making more power N/A with making boosted power. To make more peak power N/A you shift the power curve higher and lose low end torque.

With a centri boosted app, you are not going to "lose" any low end torque at all. It just will not have the gains like a twin screw. The more power you make, the more torque you will make too. The smaller the pulley on the blower, the more peak boost it will make (more peak power), but it will also make the boost come on faster, so it will have MORE low end torque. It may not be much more, but it will have more.

That is where VtecII's suggestion using a wastegate comes in. You can pulley the blower to make more peak boost than you would normally run so it comes on to boost MUCH sooner and use the wastegate to bleed off the excess boost up top.


Everyone always compares the dyno curves of a centri and PD style blower. If both 500 rwhp cars had the exact same gears (3.27s or 3.55s), weight, driver, the twin screw car should win every time. But the gearing is what plays a huge roll in that. Put a set of gears that will put the centri blower in its RPM range and now it turns into a very close race.

A properly geared centri car can be just as quick/fast as an equal RWHP TS car as long as the car is set up right.

 

[98 Saleen Cobra]

I can tell you that Centri cars are just as fast as PD.. I beat a whippled 04 with the same boost and hp as me same gearing ect.. and he was on DRs.. granted i'm a little bit lighter but he makes more tq.. get into a JT to Ysi or F1 blower car and the tq is there and a higher step up ratio in the blowers and they make power down low..