General TA on Motorway

[306maxi]

I'm sorry but it doesn't work that way. A turbo that is too small will only limit the power the engine can provide. So basically you could put an engine behind the turbo which could potentially put out 500bhp but if the turbo can only flow enough air for 400bhp then the engine will only put out 400bhp. The wastegate will take care of that.

 

[bgunn]

Unless you're in the realms of compressor surge, but no OEM will fit a turbo that's operating in that part of the compressor map to their engines, so the point is moot.

 

[306maxi]

Unless you're in the realms of compressor surge, but no OEM will fit a turbo that's operating in that part of the compressor map to their engines, so the point is moot.

Exactly. Also, giving bhp figures doesn't really give an accurate measure of engine performance, different turbo's will give different performance characteristics

This guide gives a few examples.....

http://www.uklegacy.com/forums/index.php?showtopic=93480

 

[loveshandbags]

I'm sorry but it doesn't work that way. A turbo that is too small will only limit the power the engine can provide. So basically you could put an engine behind the turbo which could potentially put out 500bhp but if the turbo can only flow enough air for 400bhp then the engine will only put out 400bhp. The wastegate will take care of that.

If you take the example of the A500 (I know nothing about Scoobies)
A500 Standard 135bhp - typically runs 145bhp
A500SS 160bhp
A500 + TMC 165bhp
A500 + TMC + Induction = 170bhp
A500SS + TMC = 170bhp
A500SS + TMC + Monza = 175bhp
All above with IHI RHF3 rated at 27-135bhp. Technically this turbo is too small for the state of the tune for all the above models bar standard.

The upgrade to the IHI RH4 for the 695 180bhp rated at 62-177bhp is correctly sized for the state of tune.

A turbo can run beyond its rated maximium for short periods hence the mapping of over boost in some cars.

On the RS Turbo II that I had in the 90's the Turbo (it was a water cooled Garett T3 needed a re-build at 70K because I had chipped the car where it was 'running' 16lbs of pressure (14.5lbs = 1 bar) - that was a lot then - standard was 7-8lbs. The IHI is possibly a better turbo.

 

[bgunn]

Turbo's aren't 'rated' for HP, they're rated for airflow at a given pressure drop, vs adiabatic efficiency. It's a complicated 'balance', but there's a great deal of tolerance on modern turbo compressor designs, with a good margin of 'error'. There are A/R ratios to think about, inducer and exducer sizes as well as lots of other variables.

You really can't compare the sizing of a turbocharger for a larger I4 engine to a parallel twin, either.

 

[loveshandbags]

Turbo's aren't 'rated' for HP, they're rated for airflow at a given pressure drop, vs adiabatic efficiency. It's a complicated 'balance', but there's a great deal of tolerance on modern turbo compressor designs, with a good margin of 'error'. There are A/R ratios to think about, inducer and exducer sizes as well as lots of other variables.

You really can't compare the sizing of a turbocharger for a larger I4 engine to a parallel twin, either.

So in your opinion - taking the example of a A500SS with a Monza running 165-170bhp - is the IHI RHF3 a correctly sized turbo ?

 

[bgunn]

I'd need to read/research a lot more than just the model of the turbo, i.e. A/R ratios, and a bit of time looking at the compressor map. I can't imagine the spec would be too far out..

 

[306maxi]

So in your opinion - taking the example of a A500SS with a Monza running 165-170bhp - is the IHI RHF3 a correctly sized turbo ?

I'm sorry but I think you're over analysing things and not really knowing the facts completely. There are plenty of people with Subaru's for instance who are running those IHI turbo's and getting a good whack more HP than the site says and they don't have problems.

 

[loveshandbags]

Interesting point, but this would just mean replacing the turbo every 3/4 years (at a guess) if that were to fail, or is there fact that smaller engines tend to suffer in general with turbo ?

Arorat - going back to your original posting - I have lifted some inputs from the Abarth section which has been acknowledged & thanked. Boosting the current turbo in the TA 85bhp to 105bhp will have the same ? over turbo life.
The turbo in the A500 has been referred to as tiny and from the test drive that I have had in both the Abarth and Twin Air the power tails off quickly. So the turbo in the TA must be tiny tiny. IF you were looking to increase the power in the Twin Air TMC Motorsport do a 'box' that can be 'hooked' in (10 minute job). The box can be set to a low number. It's easy to contact Darren on the Traders section.
To get more information on the actual Turbo used in the Twin Air you could contact IHI directly or Fiat's Technical department (need to be a dealer for this).


https://www.fiatforum.com/abarth-50...t-abarth-500c-thread-butcher-6.html?p=2812837

No good find, it's pretty simplistic & in fact IHI run an updated RHV turbo in these sizes.

It's not quite as complex as the Holset turbos run by Porsche.
What's interesting is IHI say this turbo is good on diesel engines and small capacity petrol cars & has been used on 660cc Japanese Kei cars, & is listed as working from 27-135bhp meaning it's running at top end on the 500 & beyond it in SS spec, though I'm sure it must have had durability testing done on it running the higher boost. But I'm 99% sure the aftermarket tubers getting more power from it are getting close to over speeding the turbo & creating hotter intake temps & potentially lowering power on longer runs & shortening the lifespan of the turbo.

https://www.fiatforum.com/abarth-500/230345-why-abarth-500-alfa-mito-uses-different-turbo-other-family-cars.html?p=2435722

Packaging is not an issue on the 500, the Trofeo cars use the manifold and slightly larger (it's still tiny) Garrett turbo that is fitted on GPA SS kit's.
Manifold is the same size as used on standard 500Abarth that has one of the smallest IHI turbo's I have ever seen fitted to a car. But as with many modern car s to help with quick spool up times the turbo is built into the manifold hence different part numbers for manifolds dependent on turbo configuration.
The standard turbo on a 500A is always going to hold it back to about 160ish bhp, some may claim it can do more, but by that point you would really want to look at the compressor map and check intake temps to ensure turbo is not just making hot air.
The Garrett as fitted to the Trofeo and GPA(SS) is on the Trofeo cars putting out about 215-220bhp, but is recommended to be rebuilt ever 4000klms, though of course it will be getting a hard life over those low miles, but makes you think that the road cars running this small turbo can make about the same safely, going higher again going beyond the turbo's boundaries.

Going for more power than this and wanting reliable power means getting a bigger turbo that can shift more volume of air at lower boost levels as its a balancing act between volume and pressure, you can have a little turbo moving a smaller volume of air at higher pressure which means its getting hot, will make less power than a large turbo shifting a higher volume of air at a lower temps, of course going bigger means more lag to get turbo spinning up.

Although the issues have been detailed in this thread about why the outputs are different and I agree with all said, it should be pointed out that the VL38 turbo used does not hold boost and cannot ultimately generate the same amount of sustained performance as the VL36 as found in the engines that FIAT do rate at 150BHP. This is the only practical difference between the A500/Mito engines and Bravo 150/Abarth Punto setups.

 

[306maxi]

The AC cars need their turbo's rebuilt because the cars get raced on a track and won't have as easy life as a turbo on a road car.

 

[arorat]

Thanks guys.

I am not looking to replace turbo or any part on the car, its too new. Interesting topic though.

 

[306maxi]

Thanks guys.

I am not looking to replace turbo or any part on the car, its too new. Interesting topic though.

It was quite clear to me that you were merely asking and in no way intended to modify

I don't really see the point of modifying a 1.2, 1.4 or twinair tbh. Just buy the Abarth and be done with it, or get a dismal and remap it.

 

[loveshandbags]

Thanks guys.

I am not looking to replace turbo or any part on the car, its too new. Interesting topic though.

A number of A500 drivers have found that using the TMC box has improved their mileage with some claiming to get another 3mpg. If you look at the 'figures' - purchase price is around £300 - if you wanted to sell it on you would get £200 - and I get the impression that it can be re-used on another Fiat e.g. an Abarth. Hard to recover the £100 on a 3mpg saving but over 3 years - hey - you can do the maths.
For 'safety' you could reduce the setting in case your brother with the 911 decides to 'borrow' it for the weekend.

 

[306maxi]

A number of A500 drivers have found that using the TMC box has improved their mileage with some claiming to get another 3mpg. If you look at the 'figures' - purchase price is around £300 - if you wanted to sell it on you would get £200 - and I get the impression that it can be re-used on another Fiat e.g. an Abarth. Hard to recover the £100 on a 3mpg saving but over 3 years - hey - you can do the maths.
For 'safety' you could reduce the setting in case your brother with the 911 decides to 'borrow' it for the weekend.

Not to be funny Michael, but he did say he's not looking to replace any component on his car

Some people just aren't interested in modifications to the engine. I myself am one of them tbh. I won't touch the engine in terms of modifications but I'll happily get some decent dampers fitted.

 

[loveshandbags]

Not to be funny Michael, but he did say he's not looking to replace any component on his car

Some people just aren't interested in modifications to the engine. I myself am one of them tbh. I won't touch the engine in terms of modifications but I'll happily get some decent dampers fitted.

As arorat say it's an interesting topic but a TMC box is not a replacement component - it's an add on component.

 

[pearce_jj]

A number of A500 drivers have found that using the TMC box has improved their mileage with some claiming to get another 3mpg....purchase price is around £300

Do you not think that, with all the resources of a major motor manufacturer and such a focus on emissions and economy, Fiat would be encorporating this into the design of the car in the first place, if it actually did make any MPG improvement?

 

[loveshandbags]

Do you not think that, with all the resources of a major motor manufacturer and such a focus on emissions and economy, Fiat would be encorporating this into the design of the car in the first place, if it actually did make any MPG improvement?

I have already had a turbo car re-mapped and sensible use of the 'extra power' does give improved economy. The danger is when someone starts to run the car maxed out then it can start to starve of fuel higher up or the turbo can start to run hot - as wigit as once commented 'the slippery slope'.

In terms of efficiency turbos are better than engines of equivalent power outputs in NA - one look at the A500 verus a RenaultSport demonstrates that. The A500SS with the esseesse chip has the same quoted emissions figures at 155grs/km.

The TMC box has been very successful and I get the impression that the majority of members of the 'Abarth' section are using it. TMC Motorsport would be deemed to be a very reputable company and been based in 'Ireland' I would have a bias.

Here are some comments for a member who if I remember correctly placed an order for a TA and then changed to a A500...

https://www.fiatforum.com/abarth-500/276842-500a-its-way.html?p=2816808

Yes I saw that review along with a few others that all complimented the TA for it characteristics but its MPG let it down in almost every review I read or watched.
I have a few small mods planned when I pick up the car, was going to get the alloys powder coated in white and also tint the windows at the back and possibly get a remap or TMCbox. Had a TMC box on the Bravo and it helped the MPG go up by 3-5MPG's