Handling/drive-ability for optimistic engine options.

Handling/drive-ability for optimistic engine options.

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rhosch

Original Poster:

23 posts

121 months

Thursday 27th August 2015
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Having read nearly this entire forum thread by thread, I know there have been discussions on characteristics of various forced induction options. I thought I remember specifically Stig chiming in on the PD supercharged aspect. But using the search function now and reading through dozens of threads I can't seem to find what I was looking for.

Nearing the time I can start an Ultima build (finally!), and am trying to get my thoughts in order so I can budget, have intelligent discussions with potential engine builders and know which might suit my needs best, etc. I've read all the threads on how much power is enough, I know I know, FI not needed, 500hp plenty crazy, etc. I believe you. But I'm only building one (!), the engineer in me wants the challenge as much as anything, etc.

I've driven a few fast cars, nothing with the power/weight ratio of a decent spec Ultima. I've had fun on autocross but no significant real track time (would probably start with lessons before daring to take out an Ultima of any spec).

On to the question... So general consensus I remember was big turbo bad for track, hard to manage hand of god coming out of corners and such. I don't question that.

Don't remember if there was much of a consensus on PD vs centrifugal. I've been investigating those options a bit, and have had varying opinions offered on which is best for a lightweight car. I would think constant torque of a PD like the whipple (factory seems to agree?) would be more predictable, even if the lower RPM torque makes burning the tires off even easier. Similar to a high compression race gas burning NA engine, right? Others have suggested that the more gentle linear build of boost and resultant build in torque with a centri blower might make it easier to control wheel spin from stop, coming out of a turn (?), etc. and build equal or better top end power.

Thoughts from the experts? Which would you prefer? My driving will probably be 90% street including short grocery trips and longer interstate romps (in US). A little fun on the tracks, and maybe the rare straight line challenge. Packaging wise the whipple looks great. Heat soak and cooling in general of course requires careful planning, but I would build for some fun track days, no real race use.

Storer

5,024 posts

214 months

Thursday 27th August 2015
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Don't discount a NA engine. An LS7 with a good induction and exhaust system and mild cam will give you 600hp inc the dry sump for track use.
Throttle response is instant and for 95% of owners is probably enough grunt.

A NA engine suits the car far more than a FI set-up. I have a local owner who spent a massive amount on a FI set-up and has now removed it for NA as the car was no fun to drive.

If you want to build an Ultima don't see the build as the final finished product. You can change things in the future.


Paul

rhosch

Original Poster:

23 posts

121 months

Friday 28th August 2015
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I've considered those routes and they are both still on the table. Whether I'll go NA as the final product depends on what my ultimate power goals are. 600 mild cam sounds great... but there's the 'building only one' and 'engineer in me' that will itch for more despite it being unnecessary. I know I'm not alone in that thinking.

But doing a NA base engine to which I add supercharging later is certainly one way yo go. Its tempting... kind of like the unfinished basement or attic space you can finish later... for time and financial reasons. But I do wonder about how much easier it would be to tackle location, installation, and routing of cooling components during the initial build... especially if it meant things like fuel tank modification and such.

I am pretty sure I want to avoid a mega-hp NA wild lopey aggressive cam option though, which is why I've been looking at FI.

Edited by rhosch on Friday 28th August 02:29

F.C.

3,896 posts

207 months

Friday 28th August 2015
quotequote all
rhosch said:
I've considered those routes and they are both still on the table. Whether I'll go NA as the final product depends on what my ultimate power goals are. 600 mild cam sounds great... but there's the 'building only one' and 'engineer in me' that will itch for more despite it being unnecessary. I know I'm not alone in that thinking.

But doing a NA base engine to which I add supercharging later is certainly one way yo go. Its tempting... kind of like the unfinished basement or attic space you can finish later... for time and financial reasons. But I do wonder about how much easier it would be to tackle location, installation, and routing of cooling components during the initial build... especially if it meant things like fuel tank modification and such.

I am pretty sure I want to avoid a mega-hp NA wild lopey aggressive cam option though, which is why I've been looking at FI.

Edited by rhosch on Friday 28th August 02:29
Mine is FI with centrifugal supercharger, it is very linear and I have deliberately limited it to 525-550 BHP at the contact patch.
Whipple type superchargers produce torque from way down low and in a car like this IMO it is overkill for both the weight and gearbox. I know people will say the tyres will give before the gearbox breaks but I'm afraid the problem Will be that you will ride that torque in high gears at low(ish) speed on the road and this is where the gearbox gets punished.
I too have that problem with the centrifugal charger but not to such a great extent, I have had the torque limited through the EFI but it is still very addictive to use the (remaining 500+ lbs ft )torque rather than outright power to make progress on road.
If I had my way(and the money)I would have a helical cut sequential box from an aftermarket supplier.
I have a G50/52 (bigger crown wheel) and I am scared I will break IT and my bank account.

deadscoob

2,263 posts

259 months

Friday 28th August 2015
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I think a lot of builders start off with big power intentions and from what I've seen either scale it back throughout the build or reduce the tune once it's built as they've created something which simply isn't nice to drive on road.
Any LS engined Ultima is very quick as standard and if you're going to use it for 90% on road and 10% on track think very hard about why you want the extra power (just 'cos? smile) and where you want it.
Then start thinking about what you'll need to use this extra power:
What tyres will you be running to contain the power
If road tyres like micheline ps2, how will you get the power to the road (and if you can't, where's the sweet spot between usable and a little bit of OH MY GOD!)
If something stickier, think of how the road manners will be affected
TC? Probably a good option for big house/torque engines
Gearbox and diff needs to be strong enough
Drive shafts ditto
Chassis tabs with sticky tyres were weak on pre 2013 chassis and needed upgrading if car is regularly used on track with sticky tyres
What sort of power delivery do you like, diesel like torquey, or a dammed screamer.

Think about all that, then when you have narrowed it down to a few options, think of the packaging, overall weight, fuel system needed and heat management.

I love LS7s in Ultimas, modern enough to need virtually no maintenance, have a lot of character and suit Ultimas perfectly imo.
A built 750hp screamer with Harrop induction would be perfect for me biggrin

Alternatively, LSA's are a fantastic choice. The factory commented that they're not really suitable for Ultimas but that's not true, they're just as suitable as the current supercharged offering from AS and are fantastic value for big power lumps.

Good luck!

F.C.

3,896 posts

207 months

Friday 28th August 2015
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That LSA looks cheap compared to the LS9 (at nearly twice the price), can the intake plenum rotate 180 degrees easily?

UltimaCH

3,155 posts

188 months

Friday 28th August 2015
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F.C. said:
That LSA looks cheap compared to the LS9 (at nearly twice the price), can the intake plenum rotate 180 degrees easily?
Give a ring to Auto Bionics. The have the solution for the LSA engine.

deadscoob

2,263 posts

259 months

Friday 28th August 2015
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Yep drops in and works well. Defo the bargain power plant right now, 650hp for well under the cost of an ls7.

chuntington101

5,733 posts

235 months

Friday 28th August 2015
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LSA would be a nice choice. Good power out the box and can still be upgraded down the line for more power. Block is not as strong as the LS9 but it's better than the LS3 I believe.

I also hear that the little 1.9 supercharger can be spun pretty fast! And at these higher RPMs it's not far behind it's bigger brother (2.3ltr) at all! So 650 bhp is not the upper limit of what the package can deliver.

Having said that why not install a stock LS3 to start with and get everything working? You can probably get over 500bhp with cam, exhaust and tune. Then drive it for a while until you decide on the power added you want.

UltimaFAN

107 posts

128 months

Friday 28th August 2015
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deadscoob said:
Yep drops in and works well. Defo the bargain power plant right now, 650hp for well under the cost of an ls7.
Not sure that the LSA is the bargain, the final costs will be in the same range than the LS7 solution once we consider the costs of the cooler for the compressor and other non-standard parts.

Both solutions have their different advantages/disadvantages.

deadscoob

2,263 posts

259 months

Friday 28th August 2015
quotequote all
Fair point.

But how much is an LS7 with a genuine 650hp?

An LSA with that power is about the same all in as a standard LS7?

deadscoob

2,263 posts

259 months

Friday 28th August 2015
quotequote all
LSA's as standard make peak power at 6100 with a limit shortly after at 6200 which is super conservative, a change to 6600 is easy and reliable, it uses the same heads etc as an LS3 so it can Rev like one.
That peak power is around the same as all other mildly tuned LS engines, you can check AS's specs of you like.

So I'd like to agree with you, but there's no point both of us being wrong eh? wink


Re weight, that's true, but applies to the supercharged monster AS supply too?

I'm not planning on changing, I personally love the LS7 in mine, fantastic and characterful engine. I just wish I had more power smile

xrtim

247 posts

106 months

Friday 28th August 2015
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I'm building a twin turbo ultima, the problem i have is the lack of space in the engine compartment to make it all fit, most of the parts have had to be modified to fit or made bespoke. I have learnt to Tig weld, turn and mill (well enough to do a half decent job) and bought the equipment required. You will need to think 5 steps ahead and be prepared to redesign and remake along the way, my journey started after reading this
http://www.trucktrend.com/how-to/engine/1213tr-vor...
My engine mock up is about half way through and I plan on having it running by Christmas so I can continue with the build, It has been a long and arduous journey so far but I wouldn't have it any other way
Good luck with whatever choice you make

rhosch

Original Poster:

23 posts

121 months

Friday 28th August 2015
quotequote all
Thanks guys... you are asking a lot of the same questions I have asked and will continue to ask myself.

Answer to a big one... yes, "just 'cos". smile Big part of that is the mech engineering background... the "beauty of the machine" has appeal separate from but not entirely disconnected from the driving experience.

Rambling thoughts and preferences which are somewhat an exercise in contradiction... I prefer revvy engines to big loping cams mostly based on preference of sound. But I don't mind a great throaty growl from the LS engines at all... much prefer that to a little turbo fourbanger. Reliability and durability is important, would prefer to design valvetrain to survive 8K+ rpm, and limit to 7500 or so for example. Would rather have a little boost to make HP targets (undetermined) than pushing displacement, compression, cam, and RPM to the max. Don't mind complexity as long as it isn't unnecessary or a negative in the big picture.

And while I have no intentions of putting a $100K motor in an Ultima, the cost isn't tops on my list. Dropping in a crate engine is certainly tempting for simplicity, time, and cost considerations, but I don't mind starting with the right block (OEM or aftermarket) and building an engine with quality parts, especially since I live in the heart of NASCAR and oval track country in the US and GM engine shops are literally on every corner. The price of a built engine might be same or better than an expensive crate option, like the LS9. I think my starting point, regardless of how I get to the goal, is strong block, quality internals, top end capable of surviving higher RPM if needed or especially for headroom.

Factory, thanks for the insight on the LSA vs LS9. Something I'll keep in mind even if having an engine build. Weight distribution isn't something I had considered enough I suppose.




chuntington101

5,733 posts

235 months

Friday 28th August 2015
quotequote all
xrtim said:
I'm building a twin turbo ultima, the problem i have is the lack of space in the engine compartment to make it all fit, most of the parts have had to be modified to fit or made bespoke. I have learnt to Tig weld, turn and mill (well enough to do a half decent job) and bought the equipment required. You will need to think 5 steps ahead and be prepared to redesign and remake along the way, my journey started after reading this
http://www.trucktrend.com/how-to/engine/1213tr-vor...
My engine mock up is about half way through and I plan on having it running by Christmas so I can continue with the build, It has been a long and arduous journey so far but I wouldn't have it any other way
Good luck with whatever choice you make
Where is the F'ing build thread?!?!?!?! Lol

F.C.

3,896 posts

207 months

Friday 28th August 2015
quotequote all
xrtim said:
I'm building a twin turbo ultima, the problem i have is the lack of space in the engine compartment to make it all fit, most of the parts have had to be modified to fit or made bespoke. I have learnt to Tig weld, turn and mill (well enough to do a half decent job) and bought the equipment required. You will need to think 5 steps ahead and be prepared to redesign and remake along the way, my journey started after reading this
http://www.trucktrend.com/how-to/engine/1213tr-vor...
My engine mock up is about half way through and I plan on having it running by Christmas so I can continue with the build, It has been a long and arduous journey so far but I wouldn't have it any other way
Good luck with whatever choice you make
Haha you think you have it bad squeezing that into a GTR, my mechanic friend built a twin turbo CanAm and kept the clams standard.

deadscoob

2,263 posts

259 months

Saturday 29th August 2015
quotequote all
Red LSA vs LS9 they're dimensionally the same aren't they? Smaller sc on the A and rods, valves and Pistons not quite as high quality? But weight wise etc they're nigh on identical?

UltimaCH

3,155 posts

188 months

Saturday 29th August 2015
quotequote all
xrtim said:
I'm building a twin turbo ultima, the problem i have is the lack of space in the engine compartment to make it all fit, most of the parts have had to be modified to fit or made bespoke. I have learnt to Tig weld, turn and mill (well enough to do a half decent job) and bought the equipment required. You will need to think 5 steps ahead and be prepared to redesign and remake along the way, my journey started after reading this
http://www.trucktrend.com/how-to/engine/1213tr-vor...
My engine mock up is about half way through and I plan on having it running by Christmas so I can continue with the build, It has been a long and arduous journey so far but I wouldn't have it any other way
Good luck with whatever choice you make
Now that is a build not seen very often. We want more info and pics please.

anonymous-user

53 months

Saturday 29th August 2015
quotequote all
With an electronic throttle and good mapping you can make any amount of power "driveable" imo. Even high boost turbo power these days is fairly easily mapped into a reasonably linear delivery using a few tricks!

rhosch

Original Poster:

23 posts

121 months

Sunday 30th August 2015
quotequote all
Yeah I would think that would help. In fact, I've thought about the possibility of intercepting the pedal output with a selectable voltage divider or similar to create a valet mode and perhaps a "sane don't kill myself" daily driving setting as well lol.

That's a worry for a bit further down the road, but since it came up, how is the output from pedal/input to ECU configured on say LS7 style DBW which I figure is the prevailing option for modern builds? Does the pedal act as a bank of potentiometers, or is it more sophisticated?